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SQL Server DBA Phone Interview Questions
Although no two phone interviews are the same, below outlines some potential questions to keep in mind as you prepare for a SQL Server DBA phone interview:
∑Can you explain your skill set?oEmployers look for the following:DBA (Maintenance, Security, Upgrades, Performance Tuning, etc.)
Database developer (T-SQL, SSIS, Analysis Services, Reporting Services, Crystal Reports, Service Broker, etc.)Communication skills (oral and written)oDBA's opportunity
This is your 30 second elevator pitch outlining your technical expertise and how you can benefit the organization
∑Can you explain the environments you have worked in related to the following items:oSQL Server versionsoSQL Server technologiesRelational engine, Reporting Services, Analysis Services, IntegrationServicesoNumber of SQL ServersoNumber of instancesoNumber of databasesoRange of size of databasesoNumber of DBAsoNumber of DevelopersoHardware specs (CPU’s, memory, 64 bit, SANs)
∑What are the tasks that you perform on a daily basis and how have you automated them?oFor example, daily checks could include:Check for failed processesResearch errorsValidate disk space is not lowValidate none of the databases are offline or corruptPerform database maintenance as available to do sooFor example, automation could include:Setup custom scripts to query for particular issues and email the teamWrite error messages centrally in the application and review that data
Setup Operators and Alerts on SQL Server Agent Jobs for automated job notification
∑How do you re-architect a process?oReview the current process to understand what is occurring
o Backup the current code for rollback purposeso Determine what the business and technical problems are with the process oDocument the requirements for the new process
oResearch options to address the overall business and technology needsFor example, these could include:ViewsSynonymsService BrokerSSISMigrate to a new platformUpgrade in placeo Design and develop a new solutionoConduct testing (functional, load, regression, unit, etc.)oRun the systems in paralleloSunset the existing systemoPromote the new system
∑What is your experience with third party applications and why would you use them?oExperienceBackup toolsPerformance toolsCode or data synchronizationDisaster recovery\high availabilityoWhyNeed to improve upon the functionality that SQL Server offers nativelySave time, save money, better information or notification
∑How do you identify and correct a SQL Server performance issue?oIdentification - Use native tools like Profiler, Perfmon, system stored
procedures, dynamic management views, custom stored procedures or third party toolso Analysis - Analyze the data to determine the core problems
oTesting - Test the various options to ensure they perform better and do not cause worse performance in other portions of the application
oKnowledge sharing - Share your experience with the team to ensure they understand the problem and solution, so the issue does not occur again
∑What are the dynamic management views and what value do they offer?oThe DMV's are a set of system views new to SQL Server 2005 and beyond to
gain insights into particular portions of the engineoHere are some of the DMV's and the associated value:
sys.dm_exec_query_stats and sys.dm_exec_sql_text - Buffered code in SQL Serversys.dm_os_buffer_descriptorssys.dm_tran_locks - Locking and blockingsys.dm_os_wait_stats - Wait stats
sys.dm_exec_requests and sys.dm_exec_sessions - Percentage complete for a process
∑What is the process to upgrade from DTS to SSIS packages?oYou can follow the steps of the migration wizard but you may need to manually
upgrade portions of the package that were not upgraded by the wizardoFor script related tasks, these should be upgraded to new native components or
VB.NET code∑ Problem With as many Data Transformation Services (DTS) Packages that have been developed and deployed for B2B, data integration and BI needs, when it comes to upgrading from SQL Server 2000 to 2005, this portion of the upgrade will need special attention. DTS Packages have become engrained in many applications and business processes making them business critical for not only internal applications but also mission critical for business partners. In addition, DTS Packages are probably being used in unexpected ways than originally intended further complicating the upgrade process. In some respects DTS Packages being called directly from web pages or being automatically triggered based on a business event follow a much different paradigm than those DTS Packages being called from a SQL Server Job as was probably how DTS Package execution was originally intended. With the varying usage of the SQL Server 2000 DTS Packages, what is the upgrade process to SQL Server 2005 Integration Services (SSIS) Packages?
∑ Solution The DTS Package (SQL Server 2000) to SSIS Package (SQL Server 2005) upgrade is dependent on the Business Intelligence Development Studio which
follows the Visual Studio paradigm of solutions and projects. In the example below, we will create a single solution and project with a single SSIS Package, although numerous SSIS Packages can reside in a single solution. Follow these steps to migrate your DTS Packages to SSIS Packages with the Migrate DTS 2000 Package Wizard:
I Steps Screen ShotD
1SQL Server 2000 DTS Package - The original logic is to delete data from the destination table and then import all of the data.
2Migrate DTS 2000 Package - Start the migration wizard by starting the Business Intelligence Development Studio, creating an Integration Services project and navigating to Project | Migrate DTS 2000 Package.
3Choose Source Location - Specify the SQL Server 2000 server name with the DTS Package that needs to be migrated and the authenticatio n type.
Press the 'Next >' button to continue the process.
4Choose Destination Location - Directory on your desktop to save the SSIS Package file.
Press the 'Next >' button to continue the process.
5List Packages - All DTS Packages on the SQL Server 2000 instance that can be upgraded.
Press the 'Next >' button to continue the process.
6Specify a Log File - Press the 'Browse' button to specify a log file for the migration process.
Press the 'Next >' button to continue the process.
7Complete the Wizard - Review the configuration s and then press the 'Finish' button to begin the migration process.
8Migrating the packages... - Review the status for the migration.
9Integration Services Package - Review the objects to validate the code was successfully migrated.
∑For information on deploying SSIS Packages, reference∑What are some of the features of SQL Server 2012 that you are looking into and
why are they of interest?o AlwaysONo Contained Databaseso User Defined Server Roles oNew date and time functionso New FORMAT and CONCAT functions oNew IIF and CHOOSE functionso New paging features with OFFSET and FETCHo NOTE - Many more new features do exist, this is an abbreviated list.
Keep in mind that these questions are primarily related to the relational engine, so a BI DBA would have a whole different set of questions. In addition, the more you know about the organization and role should guide you down a path for the types of questions you should be prepared for during the phone interview.
SQL Server Backup and Recovery
∑Question 1 - What are 2 options to validate whether or not a backup will restore successfully?o Restore the backup as a portion of a testing process or log shipping. oRestore the backup with the Verify Only option.
∑Question 2 - How can you issue a full backup and not interrupt the LSN's?o Issue a copy only backup.
SQL Server Performance Tuning
∑Question 1 - Name as many native SQL Server performance monitoring and tuning toolsthat you know of and their associated value.
o System objects - System objects such as sp_who2, sp_lock, fn_get_sql, etc. provide a simple means to capture basic metrics related to locking, blocking, executing code, etc.
oProfiler - In a nutshell, Profiler provides the lowest common denominator of activity on a SQL Server instance. Profiler captures per session code with the ability to filter the data collection based on database, login, host name, application name, etc. in order to assess the IO, CPU usage, time needed, etc.
oPerfmon\System Monitor - Perfmon\System Monitor is responsible for macro level metrics related to processes and sub systems.
oDynamic Management Views and Functions - New to SQL Server 2005 and beyond, the Dynamic Management Views and Functions offer a real time view into the SQL Server sub systems.
oTYPEPERF.EXE - TYPEPERF.EXE is a command line tool included with the Windows operating system that writes performance data to the command window or to a file. It is necessary to capture performance data whenever you are trying to diagnose performance issues on a server. Performance data provides informationon the server's utilization of the processor, memory, and disk, as well as SQLServer-specific performance data.
oSQL Server Management Studio Built-in Performance Reports - As part of the installation of SQL Server 2005 and beyond a number of performance-relatedreports are installed. To get to these reports open the SQL Server Management Studio (SSMS) and connect to a SQL Server instance. If you don't have an instance of Reporting Services installed then the icon will be disabled.
∑Question 2 - How do you go about tuning a SQL Server query?oIdentify the query causing the issue.
oReview the query plan by issuing SHOWPLAN_TEXT, SHOWPLAN_ALL, Graphical Query Plan or sys.dm_exec_query_stats.
oReview the individual query components to determine which components of the query have the highest cost.
oOutline options to improve the query such as moving from cursor based logic to set based logic or vice versa, changing the JOIN order, WHERE clause or ORDER BY clause, adding indexes, removing indexes, creating covering indexes,etc.o Test the options to determine the associated performance improvement. oImplement the solution.
SQL Server Maintenance
∑Question 1 - What are the three options in SQL Server 2005 and beyond to rebuild indexes?o CREATE INDEX with DROP_EXISTING oDROP INDEX and CREATE INDEXo ALTER INDEX
∑Question 2 - Name 3 or more DBCC commands and their associated purpose.
oDBCC CACHESTATS - Displays information about the objects currently in the buffer cache.
oDBCC CHECKDB - This will check the allocation of all pages in the database as well as check for any integrity issues.
oDBCC CHECKTABLE - This will check the allocation of all pages for a specific table or index as well as check for any integrity issues.
oDBCC DBREINDEX - This command will reindex your table. If the indexname is left out then all indexes are rebuilt. If the fillfactor is set to 0 then this will use the original fillfactor when the table was created.
oDBCC PROCCACHE - This command will show you information about the procedure cache and how much is being used.
oDBCC MEMORYSTATUS - Displays how the SQL Server buffer cache is divided up, including buffer activity.
oDBCC SHOWCONTIG - This command gives you information about how much space is used for a table and indexes. Information provided includes number of pages used as well as how fragmented the data is in the database.
oDBCC SHOW_STATISTICS - This will show how statistics are laid out for an index. You can see how distributed the data is and whether the index is really agood candidate or not.
oDBCC SHRINKFILE - This will allow you to shrink one of the database files. This is equivalent to doing a database shrink, but you can specify what file and the size to shrink it to. Use the sp_helpdb command along with the database name to see the actual file names used.
oDBCC SQLPERF - This command will show you much of the transaction logs are being used.
oDBCC TRACEON - This command will turn on a trace flag to capture events in the error log. Trace Flag 1204 captures Deadlock information.o DBCC TRACEOFF - This command turns off a trace flag.
SQL Server Database Design
∑Question 1 - What happens when you add a column in the middle of a table (dbo.Test1) in SQL Server Management Studio?
oManagement Studio creates a temporary table called dbo.Tmp_Test1 with the new structure.
o If there is data in the original table dbo.Test1 this data is inserted into the new temp table dbo.Tmp_Test1 (now you have two sets of the same data).o The original table dbo.Test1 is dropped.oThe new table dbo.Tmp_Test1 is renamed to dbo.Test1.oIf the table has indexes all of the indexes are recreated.
∑Question 2 - What are included columns with respect to SQL Server indexing?
oA new type of index was developed in SQL Server 2005 and beyond that assists in situations where a covering index is needed.
oIndexes with Included Columns are nonclustered indexes that have the following benefits:
Columns defined in the include statement, called non-key columns, are not counted in the number of columns by the database engine.
Columns that previously could not be used in queries, like nvarchar(max), can be included as a non-key column.A maximum of 1023 additional columns can be used as non-key columns.
SQL Server Business Intelligence
∑Question 1 - Name some new features from Data Transformation Services to SQL Server Integration Services.o SSIS checkpoints. oSSIS logging.o SSIS package configurations. oSSIS Breakpoint.o Dynamic flat file connections. oSSIS batch processing.oMERGE JOIN.
∑Question 2 - How do you backup Analysis Services databases?oCreate the XML statement to backup the Analysis Services databases, then
create a SQL Server Agent Job to perform the task on a daily basis.
∑Question 1: What sorts of functionality does SQL Server Agent provide?oSQL Server Agent is a Windows service that accompanies each instance of SQL
Server on a machine for most editions of SQL Server.oSQL Server Agent is primarily a job scheduler for executing T-SQL, SSIS,
DOS, etc. scripts.oSQL Server Agent is also responsible for defining Operators and Alerts.
Operators can be associated with Jobs or Alerts, so that particular people (email addresses, pagers, NET SEND) are notified or distribution lists are notified if an issue occurs.
Alerts can be setup for custom conditions or errors of a particular severity level.
∑Question 2: Do all of the SQL Server 2005, 2008, 2008 R2 editions install the SQL Server Agent service by default?oNo - The SQL Server Express Edition does not have a SQL Server Agent Service.
∑Question 3: If SQL Server Express does not have a job scheduling interface what alternatives are available?oWindows Task Scheduler.
oThird party solutions.
∑Question 4: True or False - Can a single Job have multiple Job Schedules?oTrue.
∑Question 5: Which database stores the SQL Server Agent objects?oMSDB
Question Difficulty = Moderate
∑ Question 1: How many options are available to identify failed jobs? oManually review the failed Jobs in Management Studio.
oSetup an automated process to query the msdb.dbo.sysjobhistory system table to find the failures.
∑Question 2: How many of the SQL Server Agent system tables can you name with their associated purpose?osysjobactivity stores data about job activity
o sysjobhistory stores data for all historical executions of all jobs osysjobs stores data about each job such as the nameo sysjobschedules stores job schedule information
o sysjobservers stores server information related to a jobosysjobsteps stores specific job step information such as the type of code
being issued, the actual code, etc.osysjobstepslogs stores specific job step log information for each run if this is
enabled.
∑Question 3: How many of the SQL Server Agent system stored procedures can you name with their associated purpose?o sp_help_job This stored procedure returns information about the job.If no parameters are used information is returned for all jobs.
If a specific job_id is passed it gives you job information, job step information, schedule information and last run information.o sp_help_jobactivity This stored procedure returns information about the status of the job run.If no parameters are used information is returned for all jobs.o sp_help_jobcount
This stored procedure gives you a count of how many jobs a schedule is tied to.This stored procedure requires either @schedule_id or @schedule_nameto be passed as a parameter.o sp_help_jobhistory
This stored procedure returns all history information for all of the job runs.
If no parameters are used information is returned for all jobs.If you also use parameter @mode = N'FULL' this provides additional
information about each job step.o sp_help_jobs_in_schedule
This stored procedure gives you a list of the jobs that are tied to a schedule.This requires either @schedule_id or @schedule_name to be passed as a
parameter.o sp_help_jobschedule
This stored procedure provides jobs schedule information for a particular job.
This stored procedure requires either @job_id or @job_name to be passed.o sp_help_jobserver
This stored procedure provides information about a specific server tied to a job.
This stored procedure requires either @job_id or @job_name to be passed.o sp_help_jobstep
This stored procedure provides information about the job steps for a specific job.
This stored procedure requires either @job_id or @job_name to be passed.o sp_help_jobsteplog This stored procedure returns information about a specific job step log.
This stored procedure requires either @job_id or @job_name to be passed.osp_get_composite_job_infoThis stored procedure returns combined data for all jobs in the system.If no parameters are used info is returned for all jobs.
∑Question 4: What resources are available to troubleshoot SQL Server Agent?
oSQL Server Agent Log is a record of all entries written by the SQL Server Agent service.
oPerformance Monitor and Profiler can be setup to monitor the status of a particular job.
∑Question 5: True or False. Besides the MSDB database, SQL Server Agent also has configuration parameter related data stored in the registry.oTrue.
Question Difficulty = Advanced
∑Question 1: What is multi-server administration and when would you use it?oJob management paradigm with a master server and one or more target servers.
The master server sends and receives jobs from the target servers with the entire job and job step related information stored on the master server. When the jobs complete on the target servers notification is sent to the master server
so this server has the updated information. Multi-server administration is used in a enterprise environment where a consistent set of jobs need to run on numerous SQL Servers, this technology helps to consolidate the creation, execution and management of those jobs.
∑Question 2: What is a SQL Server Agent Proxy? Can you name some of the sub-systemsproxies? Why are the proxies of any significance?oA SQL Server Agent Proxy is an account that is setup to help secure a particularsub-system, so that if an login\user is trying to access the particular sub-system and does not have rights, the proxy will grant rights.oThe SQL Server Agent Proxies include:ActiveX ScriptOperating System (CmdExec)Replication DistributorReplication MergeReplication Queue ReaderReplication SnapshotReplication Transaction-Log ReaderAnalysis Services Command
Analysis Services QuerySSIS Package ExecutionUnassigned Proxies
oThe SQL Server Agent Proxies offer a new level of granularity for SQL Server Agent that was not previously available.
∑Question 3: What are the new SQL Server Agent Fixed Database Roles and what is the significance of each role?oSQLAgentUserRole - Ability to manage Jobs that they own
oSQLAgentReaderRole - All of the SQLAgentUserRole rights and the ability to review multi-server jobs, their configurations and history
oSQLAgentOperatorRole - All of the SQLAgentReaderRole rights and the ability to review operators, proxies and alerts, execute, stop or start all local jobs, delete the job history for any local job as well as enable or disable all local jobs and schedules
SQL Server Backup and Recovery
∑Question 1 - What are 2 options to validate whether or not a backup will restore successfully?o Restore the backup as a portion of a testing process or log shipping. oRestore the backup with the Verify Only option.
∑Question 2 - How can you issue a full backup and not interrupt the LSN's?o Issue a copy only backup.
SQL Server Performance Tuning
∑Question 1 - Name as many native SQL Server performance monitoring and tuning toolsthat you know of and their associated value.
o System objects - System objects such as sp_who2, sp_lock, fn_get_sql, etc. provide a simple means to capture basic metrics related to locking, blocking, executing code, etc.
oProfiler - In a nutshell, Profiler provides the lowest common denominator of activity on a SQL Server instance. Profiler captures per session code with the ability to filter the data collection based on database, login, host name, application name, etc. in order to assess the IO, CPU usage, time needed, etc.
oPerfmon\System Monitor - Perfmon\System Monitor is responsible for macro level metrics related to processes and sub systems.
oDynamic Management Views and Functions - New to SQL Server 2005 and beyond, the Dynamic Management Views and Functions offer a real time view into the SQL Server sub systems.
oTYPEPERF.EXE - TYPEPERF.EXE is a command line tool included with the Windows operating system that writes performance data to the command window or to a file. It is necessary to capture performance data whenever you are trying to diagnose performance issues on a server. Performance data providesinformation on the server's utilization of the processor, memory, and disk, as well as SQL Server-specific performance data.
oSQL Server Management Studio Built-in Performance Reports - As part of the installation of SQL Server 2005 and beyond a number of performance-relatedreports are installed. To get to these reports open the SQL Server Management Studio (SSMS) and connect to a SQL Server instance. If you don't have an instance of Reporting Services installed then the icon will be disabled.
∑Question 2 - How do you go about tuning a SQL Server query?o Identify the query causing the issue.
oReview the query plan by issuing SHOWPLAN_TEXT, SHOWPLAN_ALL, Graphical Query Plan or sys.dm_exec_query_stats.
oReview the individual query components to determine which components of the query have the highest cost.
oOutline options to improve the query such as moving from cursor based logic to set based logic or vice versa, changing the JOIN order, WHERE clause or ORDER BY clause, adding indexes, removing indexes, creating covering indexes,
etc.o Test the options to determine the associated performance improvement. oImplement the solution.
SQL Server Maintenance
∑Question 1 - What are the three options in SQL Server 2005 and beyond to rebuild indexes?o CREATE INDEX with DROP_EXISTING oDROP INDEX and CREATE INDEXo ALTER INDEX
∑Question 2 - Name 3 or more DBCC commands and their associated purpose.
oDBCC CACHESTATS - Displays information about the objects currently in the buffer cache.
oDBCC CHECKDB - This will check the allocation of all pages in the database as well as check for any integrity issues.
oDBCC CHECKTABLE - This will check the allocation of all pages for a specific table or index as well as check for any integrity issues.
oDBCC DBREINDEX - This command will reindex your table. If the indexname is left out then all indexes are rebuilt. If the fillfactor is set to 0 then this will use the original fillfactor when the table was created.
oDBCC PROCCACHE - This command will show you information about the procedure cache and how much is being used.
oDBCC MEMORYSTATUS - Displays how the SQL Server buffer cache is divided up, including buffer activity.
oDBCC SHOWCONTIG - This command gives you information about how much space is used for a table and indexes. Information provided includes number of pages used as well as how fragmented the data is in the database.
oDBCC SHOW_STATISTICS - This will show how statistics are laid out for an index. You can see how distributed the data is and whether the index is really agood candidate or not.
oDBCC SHRINKFILE - This will allow you to shrink one of the database files. This is equivalent to doing a database shrink, but you can specify what file and the size to shrink it to. Use the sp_helpdb command along with the database name to see the actual file names used.
oDBCC SQLPERF - This command will show you much of the transaction logs are being used.
oDBCC TRACEON - This command will turn on a trace flag to capture events in the error log. Trace Flag 1204 captures Deadlock information.o DBCC TRACEOFF - This command turns off a trace flag.
SQL Server Database Design
∑Question 1 - What happens when you add a column in the middle of a table (dbo.Test1) in SQL Server Management Studio?
oManagement Studio creates a temporary table called dbo.Tmp_Test1 with the new structure.
o If there is data in the original table dbo.Test1 this data is inserted into the new temp table dbo.Tmp_Test1 (now you have two sets of the same data).o The original table dbo.Test1 is dropped.oThe new table dbo.Tmp_Test1 is renamed to dbo.Test1.oIf the table has indexes all of the indexes are recreated.
∑Question 2 - What are included columns with respect to SQL Server indexing?
oA new type of index was developed in SQL Server 2005 and beyond that assists in situations where a covering index is needed.
oIndexes with Included Columns are nonclustered indexes that have the following benefits:
Columns defined in the include statement, called non-key columns, are not counted in the number of columns by the database engine.
Columns that previously could not be used in queries, like nvarchar(max), can be included as a non-key column.A maximum of 1023 additional columns can be used as non-key columns.
SQL Server Business Intelligence
∑Question 1 - Name some new features from Data Transformation Services to SQL Server Integration Services.o SSIS checkpoints. oSSIS logging.o SSIS package configurations. oSSIS Breakpoint.o Dynamic flat file connections. oSSIS batch processing.oMERGE JOIN.
∑Question 2 - How do you backup Analysis Services databases?oCreate the XML statement to backup the Analysis Services databases, then
create a SQL Server Agent Job to perform the task on a daily basis.
Question Difficulty = Easy
∑Question 1: What isolation levels will provide completely read-consistent views of a database to all transactions?
oAnswer (SQL Server 2000): Only the SERIALIZABLE isolation level will provide a completely read-consistent view of a database to a given transaction.
In any of the other isolation levels, you could perceive some/all of the following, depending on the isolation level running in:Uncommitted dependency/dirty readsInconsistent Analysis/non-repeatable readsPhantom reads (via insert/delete)
oAnswer (SQL Server 2005): Both the SERIALIZABLE and SNAPSHOT isolation levels will provide a completely read-consistent view of a database to a given transaction. In any of the other isolation levels, you could perceive some/all of the following, depending on the isolation level running in:Uncommitted dependency/dirty readsInconsistent Analysis/non-repeatable readsPhantom reads (via insert/delete)
∑Question 2: Within the READ_COMMITTED isolation level, during a read operation how long are locks held/retained for?
oAnswer: When SQL Server executes a statement at the read committed isolation level, it acquires short lived share locks on a row by row basis. The duration of these share locks is just long enough to read and process each row; the server generally releases each lock before proceeding to the next row. Thus, if you run a simple select statement under read committed and check for locks, you will typically see at most a single row lock at a time. The sole purpose of these locks is to ensure that the statement only reads and returns committed data. The locks work because updates always acquire an exclusive lock which blocks any readers trying to acquire a share lock.
∑Question 3: Within the REPEATABLE_READ and SERIALIZABLE isolation levels, during a read operation and assuming row-level locking, how long are locks held/retained for?
oAnswer: Within either of these isolation levels, locks are held for the duration of the transaction, unlike within the READ_COMMITTED isolation level as noted above.
∑Question 4: Can locks ever be de-escalated?oAnswer: No, locks are only escalated, never de-
escalated. Seehttp://msdn2.microsoft.com/en-us/library/ms184286.aspx . Question Difficulty = Moderate
∑Question 1: What are the different types of lock modes in SQL Server 2000 and 2005?oAnswer:SharedUpdateExclusiveSchema (modification and stability)Bulk Update
Intent (shared, update, exclusive)Key Range (shared, insert, exclusive)∑Question 2: Can you explain scenarios where each type of lock would be taken:oAnswer:
SHARED - Used for read operations that do not change or update data, such as a SELECT statement.
UPDATE - Used on resources that can be updated. Prevents a common form of deadlock that occurs when multiple sessions are reading, locking, and potentially updating resources later. In a repeatable read or serializable transaction, the transaction reads data, acquiring a shared (S) lock on the resource (page or row), and then modifies the data, which requires lock conversion to an exclusive (X) lock. If two transactions acquire shared-modelocks on a resource and then attempt to update data concurrently, one transaction attempts the lock conversion to an exclusive
(X) lock. The shared-mode-to-exclusive lock conversion must wait because the exclusive lock for one transaction is not compatible with the shared-mode lock of the other transaction; a lock wait occurs. The second transaction attempts to acquire an exclusive (X) lock for its update. Because both transactions are converting to exclusive (X) locks, and they are each waiting for the other transaction to release its shared-mode lock, a deadlock occurs. To avoid this potential deadlock problem, update (U) locks are used. Only one transaction can obtain an update (U) lock to a resource at a time. If a transaction modifies a resource, the update (U) lock is converted to an exclusive (X) lock.
EXCLUSIVE - Used for data-modification operations, such as INSERT, UPDATE, or DELETE. Ensures that multiple updates cannot be made to the same resource at the same time.
INTENT - Used to establish a lock hierarchy. The types of intent locks are: intent shared (IS), intent exclusive (IX), and shared with intent exclusive (SIX). (Another question in the Difficult level section expands on this)
SCHEMA - Used when an operation dependent on the schema of a table is executing. The types of schema locks are: schema modification (Sch-M) and schema stability (Sch-S).
BULK UPDATE - Used when bulk copying data into a table and the TABLOCK hint is specified.
KEY RANGE - Protects the range of rows read by a query when using the serializable transaction isolation level. Ensures that other transactionscannot insert rows that would qualify for the queries of the serializable transaction if the queries were run again.∑Question 3: What is lock escalation and what triggers it?
oAnswer: The process of converting many fine-grained locks into fewer coarse- grained locks.
Escalation reduces system resource consumption/overhead while increasing the possibility of concurrency conflicts
To escalate locks, the Database Engine attempts to change the intent lock on the table to the corresponding full lock, for example, changing an intent exclusive (IX) lock to an exclusive (X) lock, or an intent shared (IS) lock to a shared (S) lock). If the lock escalation attempt succeeds and the full table lock is acquired, then all heap or B-tree, page (PAGE), key-range (KEY), orrow-level (RID) locks held by the transaction on the heap or index are released. If the full lock cannot be acquired, no lock escalation happens at that time and the Database Engine will continue to acquire row, key, or page locks.
Lock escalation is triggered at either of these times:When a single Transact-SQL statement acquires at least 5,000 locks on a
single table or index.When the number of locks in an instance of the Database Engine exceeds
memory or configuration thresholds.If locks cannot be escalated because of lock conflicts, the Database Engine
periodically triggers lock escalation at every 1,250 new locks acquired.∑Question 4: Name as many of the lockable resources as possible in SQL Server 2005?oAnswer:RID (single row on a heap)KEY (single row (or range) on an index)PAGEEXTENTHOBT (heap or b-tree)TABLE (entire table, all data and indexes)FILEAPPLICATIONMETADATAALLOCATION_UNITDATABASE
∑Question 5: What requirements must be met for a BULK-UPDATE lock to be granted, and what benefit do they serve?
oAnswer: The Database Engine uses bulk update (BU) locks when bulk copying data into a table, and either the TABLOCK hint is specified or the table lock on bulk load table option is set using sp_tableoption. Bulk update (BU) locks allow multiple threads to bulk load data concurrently into the same table while preventing other processes that are not bulk loading data from accessing the table.
∑Question 6: What is the least restrictive type of lock? What is the most restrictive?
oAnswer: The least restrictive type of lock is a shared lock. The most restrictive type of lock is a schema-modification∑Question 7: What is a deadlock and how is it different from a standard block situation?
oAnswer: A deadlock occurs when two or more tasks permanently block each other by each task having a lock on a resource which the other tasks are trying to lock. In a deadlock situation, both transactions in the deadlock will wait forever unless the deadlock is broken by an external process – in a standard blocking scenario, the blocked task will simply wait until the blocking task releases the conflicting lock scenario.
∑Question 8: Which 2 isolation levels support optimistic/row-versioned-basedconcurrency control?
oAnswer: First is the the READ COMMITTED isolation level. This is the only level that supports both a pessimistic (locking-based) and optimistic (version- based) concurrency control model. Second is SNAPSHOT isolation level that supports only an optimistic concurrency control model.∑Question 9: What database options must be set to allow the use of optimistic models?
oAnswer: READ_COMMITTED_SNAPSHOT option for the read committed optimistic model. ALLOW_SNAPSHOT_ISOLATION option for the snapshot isolation level∑Question 10: What is the size of a lock structure?oAnswer: 96 bytes
Question Difficulty = Difficult
∑Question 1: In what circumstances will you see key-range locks, and what are theymeant to protect against?
o Answer: You will only see key-range locks when operating in the SERIALIZABLE isolation level.
o Key-range locks protect a range of rows implicitly included in a record set being read by a Transact-SQL statement. The serializable isolation level requires that any query executed during a transaction must obtain the same set of rows every time it is executed during the transaction. A key range lock protects this requirement by preventing other transactions from inserting new rows whose keys would fall in the range of keys read by the serializable transaction.
oKey-range locking prevents phantom reads. By protecting the ranges of keys between rows, it also prevents phantom insertions into a set of records accessed by a transaction.∑Question 2: Explain the purpose of INTENT locks?
oAnswer: The Database Engine uses intent locks to protect placing a shared (S) lock or exclusive (X) lock on a resource lower in the lock hierarchy. Intent locks are named intent locks because they are acquired before a lock at the lower level, and therefore signal intent to place locks at a lower level. Intent locks serve two purposes:
To prevent other transactions from modifying the higher-level resource in a way that would invalidate the lock at the lower level.To improve the efficiency of the Database Engine in detecting lock conflicts
at the higher level of granularity.∑Question 3: Can deadlocks occur on resources other than database object?oAnswer: YES.∑Question 4: What are the different types of resources that can deadlock?
oAnswer: Deadlock is a condition that can occur on any system with multiple threads, not just on a relational database management system, and can occur for resources other than locks on database objects. Here are the resources:
Locks - Waiting to acquire locks on resources, such as objects, pages, rows, metadata, and applications can cause deadlock.
Worker threads - A queued task waiting for an available worker thread can cause deadlock. If the queued task owns resources that are blocking all worker threads, a deadlock will result
Memory - When concurrent requests are waiting for memory grants that cannot be satisfied with the available memory, a deadlock can occur.
Parallel query execution-related resources - Coordinator, producer, or consumer threads associated with an exchange port may block each other causing a deadlock usually when including at least one other process that is not a part of the parallel query. Also, when a parallel query starts execution, SQL Server determines the degree of parallelism, or the number of worker threads, based upon the current workload. If the system workload unexpectedly changes, for example, where new queries start running on the server or the system runs out of worker threads, then a deadlock could occur.
Multiple Active Result Sets (MARS) resources - Resources used to control interleaving of multiple active requests under MARS, including:
User resource - when a thread is waiting for a resource that is potentially controlled by a user application, the resource is considered to be an external or user resource and is treated like a lock
Session mutex - The tasks running in one session are interleaved, meaning that only one task can run under the session at a given time. Before the task can run, it must have exclusive access to the session mutex.
Transaction mutex - All tasks running in one transaction are interleaved, meaning that only one task can run under the transaction at a given time. Before the task can run, it must have exclusive access to the transaction mutex.
∑Question 5: Explain how the database engine manages the memory footprint for the lock pool when running in a dynamic lock management mode.
oAnswer (SQL Server 2000): When the server is started with locks set to 0, the lock manager allocates two percent of the memory allocated to SQL Server to an initial pool of lock structures. As the pool of locks is exhausted, additional locks are allocated. The dynamic lock pool does not allocate more than 40 percent of the memory allocated to SQL Server.
Generally, if more memory is required for locks than is available in current memory, and more server memory is available (the max servermemory threshold has not been reached), SQL Server allocates memory dynamically to satisfy the request for locks. However, if allocating that memory would cause paging at the operating system level (for example, if another application was running on the same computer as an instance of SQL Server and using that memory), more lock space is not allocated.
oAnswer (SQL Server 2005): When running in dynamic management mode (i.e. if the the server is started with locks configuration option set to 0), the lock manager acquires sufficient memory from the Database Engine for an initial pool of 2,500 lock structures. As the lock pool is exhausted, additional memory is acquired for the pool.
Generally, if more memory is required for the lock pool than is available in the Database Engine memory pool, and more computer memory is available (the max server memory threshold has not been reached), the Database Engine allocates memory dynamically to satisfy the request for locks. However, if allocating that memory would cause paging at the operating system level (for example, if another application is running on the same computer as an instance of SQL Server and using that memory), more lock space is not allocated. The dynamic lock pool does not acquire more than 60 percent of the memory allocated to the Database Engine. After the lock pool has reached 60 percent of the memory acquired by an instance of the Database Engine, or no more memory is available on the computer, further requests for locks generate an error.
∑Question 6: Describe the differences between the pessimistic SERIALIZABLE model and the optimistic SNAPSHOT model in terms of transactional isolation (i.e., not the concurrency differences, but instead how the exact same transactional modifications may result in different final outcomes).oAnswer:
o It is typically relatively simple to understand SERIALIZABLE. For the outcome of two transactions to be considered SERIALIZABLE, it must be
possible to achieve this outcome by running one transaction at a time in some order.o Snapshot does not guarantee this level of transactional isolation.oImagine the following sample scenario:
There is a bag containing a mixture of white and black marbles. Suppose that we want to run two transactions. One transaction turns each of the white marbles into black marbles. The second transaction turns each of the black marbles into white marbles. If we run these transactions under SERIALIZABLE isolation, we must run them one at a time. The first transaction will leave a bag with marbles of only one color. After that, the second transaction will change all of these marbles to the other color. There are only two possible outcomes: a bag with only white marbles or a bag with only black marbles.
If we run these transactions under snapshot isolation, there is a third outcome that is not possible under SERIALIZABLE isolation. Each transaction can simultaneously take a snapshot of the bag of marbles as it
exists before we make any changes. Now one transaction finds the white marbles and turns them into black marbles. At the same time, the other transactions finds the black marbles - but only those marbles that where black when we took the snapshot - not those marbles that the first transaction changed to black - and turns them into white marbles. In the end, we still have a mixed bag of marbles with some white and some black. In fact, we have precisely switched each marble.
Question Difficulty = Easy
∑Question 1: Consider a scenario where you issue a full backup. Then issue some transaction log backups, next a differential backup, followed by more transaction log backups, then another differential and finally some transaction log backups. If the SQL Server crashes and if all the differential backups are bad, when is the latest point in time you can successfully restore the database? Can you recover the database to the current
point in time without using any of the differential backups?oAnswer: You can recover to the current point in time, as long as you have all the
transaction log backups available and they are all valid. Differential backups do not affect the transaction log backup chain.
∑Question 2: Assume the same scenario, however instead of issuing differential backups, all three of the differential backups were full backups. Assume all the full backups are corrupt with the exception of the first full backup. Can you recover the database to the current point in time in this scenario?oAnswer: Yes, just as it is with question 1. Full backups do not affectthe transaction log backup chain. As long as you have all of the transaction log backups and they are valid, you can restore the first full backup and then all subsequent transaction log backups to bring the database current.
∑Question 3: What methods are available for removing fragmentation of any kind on an index in SQL Server?oAnswer (SQL Server 2000):DBCC INDEXDEFRAGDBCC DBREINDEXCREATE INDEX…DROP EXISTING (cluster)DROP INDEX; CREATE INDEX
oAnswer (SQL Server 2005): The same processes as SQL Server 2000, only different syntaxALTER INDEX...REORGANIZEALTER INDEX...REBUILDCREATE INDEX...DROP EXISTING (cluster)DROP INDEX; CREATE INDEX
Question Difficulty = Moderate
∑Question 1: What is the fundamental unit of storage in SQL Server data files and what is it’s size?o Answer: A page with a size of 8k.
∑Question 2: What is the fundamental unit of storage in SQL Server log files and what is it’s size?o Answer: A log record, size is variable depending on the work being performed.∑Question 3: How many different types of pages exist in SQL Server?oAnswer:DataIndexText/Image (LOB, ROW_OVERFLOW, XML)GAM (Global Allocation Map)SGAM (Shared Global Allocation Map)PFS (Page Free Space)IAM (Index Allocation Map)BCM (Bulk Change Map)DCM (Differential Change Map)
Question Difficulty = Difficult
∑Question 1: What are the primary differences between an index reorganization and an index rebuild?oAnswer:
A reorganization is an "online" operation by default; a rebuild is an "offline" operation by defaultA reorganization only affects the leaf level of an index
A reorganization swaps data pages in-place by using only the pages already allocated to the index; a rebuild uses new pages/allocations
A reorganization is always a fully-logged operation; a rebuild can be aminimally-logged operation
A reorganization can be stopped mid-process and all completed work is retained; a rebuild is transactional and must be completed in entirety to keep changes
∑Question 2: Can you explain the differences between a fully-logged and minimally- logged operations?
oAnswer: In a fully logged bulk operation, depending on the type of operation being performed, SQL Server will log either each record as it is processed (when performing a bulk data-load for example), or an image of the entire page that was changed (when performing a re-index/create index for example). In a minimally- logged operation, SQL Server will log space allocations only, and also flip bitvalues in the BCM pages, assuming they are not already flipped, for extents that are modified during the bulk operation.
o This minimizes both the space required to bulk log operations during the execution of the operation, and also the time required to complete the bulk operation, since very little data is logged and updated compared to a fully-logged scenario.
oWhen a database is bulk-changeable (i.e. in the bulk-logged recovery model), the BCM pages are reset when the first "BACKUP LOG" operation occurs following the given bulk operation. During this transaction log backup, the extents that aremarked as modified in the BCM pages are included, in their entirety within the transaction log backup. This results in a much larger transaction log backup than would be expected for the size of the active transaction log. This is what allows you to recover a bulk-logged operation if you have the transaction log backup following the operation despite the fact that during the operation you are logging only space allocations.
Question Difficulty = Easy
∑Question 1: Name five different tools which can be used for performance tuning and their associated purpose.
oPerformance Monitor\System Monitor - Tool to capture macro level performance metrics.
oProfiler - Tool to capture micro level performance metrics based on the statements issued by a login, against a database or from host name.
oServer Side Trace - System objects to write the detailed statement metrics to a table or file, similar to Profiler.
oDynamic Management Views and Functions - SQL Server objects with low level metrics to provide insight into a specific portion of SQL Server i.e. the database engine, query plans, Service Broker, etc.
oManagement Studio's Built-In Performance Reports - Ability to capture point in time metrics as pre-defined by Microsoft.
oCustom scripts - Custom scripts can be developed to monitor performance, determine IO usage, monitor fragmentation, etc. all in an effort to improve performance.
oThird party applications - Performance monitoring and tuning applications from vendors in the SQL Server community.
∑Question 2: Explain how the hardware running SQL Server can help or hinder performance.oTaxed CPUs will queue requests and hinder query performance.oInsufficient memory could cause paging resulting in slow query performance.oIncorrectly configured disk drives could exacerbate IO problems.
∑Question 3: Why is it important to avoid functions in the WHERE clause?oBecause SQL Server will scan the index or the table as opposed to seeking the
data. The scan operation is a much more costly operation than a seek.oOften a slightly different approach can be used to prevent using the function in
the WHERE clause yielding a favorable query plan and high performance.
∑Question 4: How is it possible to capture the IO and time statistics for your queries?
oUse the SET STATISTICS IO and SET STATISTICS TIME settings in your queries or enable the settings in your Management Studio session.
∑Question 5: True or False - It is possible to correlate the Performance Monitor metrics with Profiler data in a single SQL Server native product?o True - This functionality is possible with SQL Server Profiler.
Question Difficulty = Moderate
∑Question 1: How can I/O statistics be gathered and reviewed for individual database files?o By using the fn_virtualfilestats function to capture the metrics.
oThis process can be automated with a script to determine the file usage with numerous samples.
∑Question 2: What is a query plan and what is the value from a performance tuning perspective?
oA query plan is the physical break down of the code being passed to the SQL Server optimizer.
oThe value from a performance tuning perspective is that each component of the query can be understood and the percentage of resource utilization can be determined at a micro level. As query tuning is being conducted, the detailed metrics can be reviewed to compare the individual coding techniques to determine the best alternative.
∑Question 3: True or False - It is always beneficial to configure TempDB with an equal number of fixed sized files as the number of CPU cores.oFalse - With always being the operative word in the question.
oDepending on the version of SQL Server, the disk subsystem, load, queries, etc., a 1 to 1 ratio of files to cores may be necessary on high end SQL Servers withintense processing.
oIf you do not have that luxury, a starting point may to be having half the number of tempdb files as compared to CPU cores.
oThis is a configuration to load test and monitor closely depending on the type of processing, load, hardware, etc. that your SQL Server is expected to support.
∑Question 4: Explain the NOLOCK optimizer hint and some pros\cons of using the hint.
oThe NOLOCK query hint allows SQL Server to ignore the normal locks that are placed and held for a transaction allowing the query to complete without having to wait for the first transaction to finish and therefore release the locks.oThis is one short term fix to help prevent locking, blocking or deadlocks.
oHowever, when the NOLOCK hint is used, dirty data is read which can compromise the results returned to the user.
∑Question 5: Explain three different approaches to capture a query plan.oSHOWPLAN_TEXT
o SHOWPLAN_ALLo Graphical Query Plan
osys.dm_exec_query_optimizer_info
o sys.dm_exec_query_plano sys.dm_exec_query_stats
Question Difficulty = Advanced
∑Question 1: True or False - A LEFT OUTER JOIN is always faster than a NOT EXISTS statement.o False - With always being the operative word. Depending on the situation the
OUTER JOIN may or may not be faster than a NOT EXISTS statement. It is necessary to test the techniques, review the query plans and tune the queries accordingly.
∑Question 2: Name three different options to capture the input (code) for a query in SQL Server.o DBCC INPUTBUFFER ofn_get_sqlosys.dm_exec_sql_text
∑Question 3: Explain why the NORECOMPUTE option of UPDATE STATISTICS is used.
oThis command is used on a per table basis to prevent the table from having statistics automatically updated based on the 'Auto Update Statistics' databaseconfiguration.
oTaking this step will prevent UPDATE STATISTICS from running during an unexpected time of the day and cause performance problems.
oBy setting this configuration it is necessary to manually UPDATE STATISTICS on a regular basis.
∑Question 4: Explain a SQL Server deadlock, how a deadlock can be identified, how it is a performance problem and some techniques to correct deadlocks.
oA deadlock is a situation where 2 spids have data locked and cannot release their lock until the opposing spid releases their lock. Depending on the severity of the deadlock, meaning the amount of data that is locked and the number of spids thatare trying to access the same data, an entire chain of spids can have locks and cause a number of deadlocks, resulting in a performance issue.
oDeadlocks can be identified by Profiler in either textual, graphical or XML format.
oDeadlocks are a performance problem because they can prevent 2 or more processes from being able to process data. A deadlock chain can occur and impact hundreds of spids based on the data access patterns, number of users,object dependencies, etc.
oDeadlocks could require a database design change, T-SQL coding change to access the objects in the same order, separating reporting and OLTP applications, including NOLOCK statements in SELECT queries that can accept dirty data, etc.
∑Question 5: Please explain why SQL Server does not select the same query plan every time for the same code (with different parameters) and how SQL Server can be forced touse a specific query plan.
oThe query plan is chosen based on the parameters and code being issued to the SQL Server optimizer. Unfortunately, a slightly different query plan can cause
the query to execute much longer and use more resources than another query with exactly the same code and only parameter differences.
oThe OPTIMIZE FOR hint can be used to specify what parameter value we want SQL Server to use when creating the execution plan. This is a SQL Server 2005 and beyond hint.
EASY
1)What is SQL Server replication?
∑Replication is subset of SQL Server that can move data and database objects in an automated way from one database to another database. This allows users to work with the same data at different locations and changes that are made are transferred to keep the databases synchronized.
2)What are the different types of SQL Server replication?
∑Snapshot replication - As the name implies snapshot replication takes a snapshot of the published objects and applies it to a subscriber. Snapshot replication completely overwrites the data at the subscriber each time a snapshot is applied. It is best suited for fairly static data or if it's acceptable to have data out of sync between replication intervals. A subscriber does not always need to be connected, so data marked for replication can be applied the next time the subscriber is connected. An example use of snapshot replication is to update a list of items that only changes periodically.
∑Transactional replication – As the name implies, it replicates each transaction for the article being published. To set up transactional replication, a snapshot of the publisher or a backup is taken and applied to the subscriber to synchronize the data. After that, when a transaction is written to the transaction log, the Log Reader Agent reads it from the transaction log and writes it to the distribution database and then to the subscriber. Only committed transactions are replicated to ensure data consistency. Transactional replication is widely applied where high latency is not allowed, such as an OLTP system for a bank or a stock trading firm, because you always need real-time updates of cash or stocks.
∑Merge replication – This is the most complex types of replication which allows changes to happen at both the publisher and subscriber. As the name implies, changes are merged to keep data consistency and a uniform set of data. Just like transactional replication, an initial synchronization is done by applying snapshot. When a transaction occurs at the Publisher or Subscriber, the change is written to change tracking tables. The Merge Agent checks these tracking
tables and sends the transaction to the distribution database where it gets propagated. The merge agent has the capability of resolving conflicts thatoccur during data synchronization. An example of using merge replication can be a store with many branches where products may be centrally stored in inventory. As the overall inventory is reduced it is propagated to the other stores to keep the databases synchronized.
3)What is the difference between Push and Pull Subscription?
∑Push - As the name implies, a push subscription pushes data from publisher to the subscriber. Changes can be pushed to subscribers on demand, continuously, or on a scheduled basis.
∑Pull - As the name implies, a pull subscription requests changes from the Publisher. This allows the subscriber to pull data as needed. This is useful for disconnected machines such as notebook computers that are not always connected and when they connect they can pull the data.
4)What are different replication agents and what’s their purpose?
∑Snapshot Agent- The Snapshot Agent is used with all types of replication. It prepares the schema and the initial bulk copy files of published tables and other objects, stores the snapshot files, and records information about synchronization in the distribution database. The Snapshot Agent runs at the Distributor.
∑Log Reader Agent - The Log Reader Agent is used with transactional replication. It moves transactions marked for replication from the transaction log on the Publisher to the distribution database. Each databasepublished using transactional replication has its own Log Reader Agent that runs on the Distributor and connects to the Publisher (the Distributor can be on the same computer as the Publisher)
∑Distribution Agent - The Distribution Agent is used with snapshot replication and transactional replication. It applies the initial snapshot to the Subscriber and moves transactions held in the distribution database to Subscribers. The Distribution Agent runs at either the Distributor for push subscriptions or at the Subscriber for pull subscriptions.
∑Merge Agent - The Merge Agent is used with merge replication. It applies the initial snapshot to the Subscriber and moves and reconciles incremental data changes that occur. Each merge subscription has its own Merge Agent that connects to both the Publisher and the Subscriber and updates both. The
Merge Agent runs at either the Distributor for push subscriptions or the Subscriber for pull subscriptions.
∑Queue Reader Agent - The Queue Reader Agent is used with transactional replication with the queued updating option. The agent runs at the Distributor and moves changes made at the Subscriber back to thePublisher. Unlike the Distribution Agent and the Merge Agent, only one instance of the Queue Reader Agent exists to service all Publishers and publications for a given distribution database.5)Does a specific recovery model need to be used for a replicated database?
∑Replication is not dependent on any particular recovery model. A database can participate in replication whether it is in simple, bulk-logged, or full. However how data is tracked for replication depends on the type of replication used.
Medium
1)What type of locking occurs during the Snapshot generation?
∑Locking depends on the type of replication used:oIn snapshot replication, the snapshot agent locks the object during the entire
snapshot generation process.oIn transactional replication, locks are acquired initially for a very brief time and
then released. Normal operations on a database can continue after that.oIn merge replication, no locks are acquired during the snapshot generation
process.
2)What options are there to delete rows on the publisher and not on the subscriber?
∑One option is to replicate stored procedure execution instead of the actual DELETE command. You can create two different versions of the stored procedures one on the publisher that does the delete and the other on the subscriber that does not do the delete.∑Another option is to not replicate DELETE commands.
3)Is it possible to run multiple publications and different type of publications from the same distribution database?
∑Yes this can be done and there are no restrictions on the number or types of publications that can use the same distribution database. One thing to note though is that all publications from a Publisher must use the same Distributor and distribution database.
4)Data is not being delivered to Subscribers, what can be the possible reasons?
∑There are a number of possible causes for data not being delivered to Subscribers:oThe table is filtered, and there are no changes to deliver to a given Subscriber.o One or more agents are not running or are failing with an error.o Data is deleted by a trigger, or a trigger includes a ROLLBACK statement.
oA transactional subscription was initialized without a snapshot, and changes have occurred on the Publisher since the publication was created.
oReplication of stored procedure execution for a transactional publication produces different results at the Subscriber.
oThe INSERT stored procedure used by a transactional article includes a condition that is not met.
o Data is deleted by a user, a replication script, or another application.
5)Explain what stored procedure sp_replcounters is used for?
∑Sp_replcounters is a system stored procedure that returns information about the transaction rate, latency, and first and last log sequence number (LSN) for each publication on a server. This is run on the publishing server. Running this stored procedure on a server that is acting as the distributor or subscribing to publications from another server will not return any data
Hard
1)How will you monitor replication latency in transactional replication?
∑Tracer tokens were introduced with SQL Server 2005 transactional replication as a way to monitor the latency of delivering transactions from the publisher to the distributor and from the distributor to the subscriber(s).
2)If I create a publication with one table as an article, and then change the schema of the published table (for example, by adding a column to the table), will the new schema ever be applied at the Subscribers?
∑Yes. Schema changes to tables must be made by using Transact-SQL or SQL Server Management Objects (SMO). When schema changes are made in SQL Server Management Studio, Management Studio attempts to drop and re-create the table and since you cannot drop published objects, the schema change will fail.
3)Is it possible to replicate data from SQL Server to Oracle?
∑Yes this can be done using heterogeneous replication. In SQL Server 2000, publishing data to other databases such as DB2 or Oracle was supported;
however, publishing data from other databases was not supported without custom programming. In SQL Server 2005 and later versions, Oracle databases can be directly replicated to SQL Server in much the same way as standard SQL Server replication.
4)How will you monitor replication activity and performance? What privilege do you need to use replication monitor?
∑The easiest way to monitor replication activity and performance is to use replication monitor, but you can also use the below tools to monitor replication performance:o T-SQL commands.o Microsoft SQL Server Management studio.∑To monitor replication, a user must be a member of the sysadmin fixed server role at theDistributor or a member of the replmonitor fixed database role in the distribution database. A system administrator can add any user to the replmonitor role, which allows that user to view replication activity in Replication Monitor; however, the user cannot administer replication.5)Can you tell me some of the common replication DMV’s and their use?
∑sys.dm_repl_articles - Contains information about each article being published. It returns data from the database being published and returns a row for each object being published in each article.
∑sys.dm_repl_schemas – Contains information about each table and column being published. It returns data from the database being published and returns one row for each column in each object being published
∑sys.dm_repl_traninfo - Contains information about each transaction in a transactional replication
