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Everything You Ever Wanted to Know About Migrating
From Informix to DB2*But were afraid to ask
J.Warren DonovanBob Carts
Everything You Ever Wanted to Know About Migrating from Informix to DB2
Bob CartsSenior Data Engineer, SAIC [email protected]
J. Warren DonovanSenior Software Engineer, [email protected]
About SAIC
42,000 Employees Headquarters in San Diego Largest Site is Washington, DC Area Majority of Work is Federal www.saic.com
About Us
Certified Informix DBAs Certified DB2 DBAs WAIUG Board of Directors Windows and UNIX (Solaris, IBM AIX, HP-
UX) IDS 7.31, 9.21, 9.3, XPS 8.31, DB2 8.1 Data Warehouse and OLTP Applications
About Our Project
Data Warehouse Multi-Node 1800+ Aggressive Users 600+ DSS Queries per day Converted from Informix XPS version 8.31
to DB2 version 8.1 900 GB of data 684 pieces of ETL code ETL code SQL, KSH, PERL
What is in this Session?
Goal: To provide basic information on differences between Informix and DB2 SQL to help you get started in evaluating, planning or executing a conversion
Assumption: You are familiar with Informix
Included:HOW to migrate Not Included:WHY …or why not
What is in this Session?
Will cover: Converting DDL Creating disk / tablespace
structures Creating Memory Structures Basic Configuration / Tuning and, Migration of SQL Code
Similarities of Informix and DB2
Relational Databases Both owned by IBM Both available for most platforms Connect to a wide variety of front
ends
Product Differences
INFORMIX Different products
for different uses Simple
configuration Simple
performance tuning
DB2 “One product fits all” Complex
configuration options Advanced and robust
performance tuning toolset
Will still exist in 10 years
Definitions – Some DB2 Speak
DBSpaces = Tablespaces Chunks = Containers Coservers = Logical PartitionsLogical Partitions are the biggest
difference between Informix 7.x / Informix 9.x and DB2.
What’s a Logical Partition? A virtual Database server A DB2 Database uses Logical Partitions (or LPs) to
maximize parallel processing by spreading data across I/O and CPUs
LPs can be used to spread data across multiple physical servers
Can be used to overcome tablespace size limitations
Can be used to overcome 2GB Memory Limitations of 32-bit installs
Before you do anything, decide if you will be using a Single or Multiple LP install!
Informix vs. DB2 StructureInformix System
Instances
BuffersMGM
Memory DBspaces
Tables
Indexes
Tables
Indexes
Databases
SHEAPTHRESMemory
Tables
Indexes
Tables
Indexes
Databases
InstancesDB2 System
Tblspaces
Buffers Buffers
Tblspaces
Warren’s Setup OrderFrom Informix1. Layout Disk (create space
for binaries - minimum)2. Install Informix3. Setup onconfig4. Start instance5. Create database6. Create dbspaces7. Update / Run DDL8. Load Data
To DB21. Layout Disk (create space for
binaries and DB at minimum)2. Install DB23. Start Instance4. Setup DBM CFG5. Create database6. Setup DB CFG7. Create memory structures8. Create tablespaces9. Update / Run DDL10. Load Data
Warren’s DB2 Migration Order
From Informix To DB21. Pick DB2 installation: Single or Multi Partition2. Get Informix DDL – Convert to DB23. Analyze DDL for Tablespace Structure4. Create DDL for Tablespaces5. Analyze Tablespaces for Memory Structure6. Create Memory DDL7. Create Instance8. Create Database9. Update / Run DDL10. Load Data11. Monitor and Tune Database
Migrating DDL The first step is to rewrite Informix DDL to
DB2 Get Informix DDL using dbschema Data types, Primary and Secondary keys
remarkably similar Extent sizes, Indexes,
Fragmentation/Partitioning are not. Know what tables you want together, and
if you will install a Single or Multiple Partition DB2 instance
Creating Tables ComparisonINFORMIX Can set initial and
next extent sizes Can fragment across
dbspaces Fragment by round-
robin, expression + hash
Can create indexes later in any dbspace
DB2 Extent size set by
tablespace 1 Table to 1 Tablespace Hash fragment in multi-
partition, round-robin automatic in a tablespace with multiple containers
Set index location in create table statement
Creating Tables Basically, all the same data types One table – one tablespace Must specify index location during create
table statement If you’ll ever need to do unlogged updates
or inserts, use the “not logged initially” option
A Partitioning Key is a good idea, especially if creating the table in a tablespace with containers that span multiple Logical Partitions
Informix Create Table Statement
CREATE TABLE NHL.PLAYERS (
NAME CHAR(20) ,
TEAM VARCHAR (20)
GOALS INTEGER ,
ASSISTS INTEGER ,
ID_NUMBER INTEGER )
FRAGMENT BY ROUND ROBIN IN bigspace
EXTENT SIZE 10000 NEXT SIZE 1000;
DB2 Create Table Statement CREATE TABLE NHL.PLAYERS ( NAME CHAR(20) ,
TEAM VARCHAR (20) GOALS INTEGER , ASSISTS INTEGER , ID_NUMBER INTEGER ) PARTITIONING KEY (ID_NUMBER) IN BIGSPACE_1 INDEX IN BIG_INDEX_1 NOT LOGGED INITIALLY ;
About Partitioning Keys The more diverse the data in a field,
and the more it is used in joins, the better
Defaults to PK (first column if no PK) Greatest performance boost is from
co-located joins: when it can join to another table on the same key, and can therefore ignore whole containers
Creating Indexes You WILL need indexes Location is determined during table
definition Be sure to use the ALLOW REVERSE
SCANS parameter Can use the db2advis tool to
recommend indexes
Sample DB2 Create Index Statement
CREATE INDEX NHL.PLAY_ID ON NHL.PLAYERS (ID_NUMBER ASC)
PCTFREE 5 ALLOW REVERSE SCANS;
With Tables Ready…Time to Setup Tablespaces Once table DDL is complete,
analyze it for tablespaces One table fits into one and ONLY
one tablespace Tablespaces can hold multiple
tables Tablespaces must have one, and
only one, memory buffer pool
Informix Dbspaces vs DB2 Tablespaces DBspaces Raw Devices, Cooked
Can add chunks Writes consecutively to
chunks Tables can be fragmented
across DBSpaces Extents set at TABLE
creation time Can offset in raw devices Can mirror at DB level
Tablespaces DMS Raw,DMS
Cooked,and SMS Can add containers Automatically balances
data across containers 1 Table to 1 Tablespace Extents set at
tablespace level Cannot offset in raw
devices No DB mirroring
Initial Disk LayoutDB2 has 3 types of tablespaces System Managed Space (for database,
tempspace and blob/clobs) Raw Database Managed Space (DMS Raw) “Cooked” Database Managed Space (DMS
Cooked)Know when to use which, and why! DB2 has no internal DB mirroring: use OS
mirroring. DB2 cannot set offsets on raw devices:
one container to one raw device
Maximum Tablespace Sizes True for all tablespace types Max size per logical partition the
tablespace spans: With 4KB pages– 64GB With 8KB pages– 128GB With 16KB pages – 256GB With 32KB pages – 512GB
Max of 255 rows per page
Choosing a Tablespace type
DMS Fastest Can add containers Cannot contain LOBsSMS Very flexible, very easy to set up Cannot add containers Can contain LOBs
Creating a simple DMS Raw TablespaceCREATE REGULAR TABLESPACE REFERENCE IN DATABASE PARTITION GROUP REF_GRP PAGESIZE 8192 MANAGED BY DATABASE
USING (DEVICE '/dev/reference_part1'131072) ON DBPARTITIONNUMS (1)
EXTENTSIZE 240 PREFETCHSIZE 240 BUFFERPOOL REF_8K OVERHEAD 12.500000 TRANSFERRATE 0.300000;
Creating a simple DMS Cooked TablespaceCREATE REGULAR TABLESPACE REF2 IN DATABASE PARTITION GROUP REF_GRP PAGESIZE 8192 MANAGED BY DATABASE
USING (FILE '/dev/ref2_part1.dat'131072) ON DBPARTITIONNUMS (1)
EXTENTSIZE 240 PREFETCHSIZE 240 BUFFERPOOL REF_8K OVERHEAD 12.500000 TRANSFERRATE 0.300000;
DMS Tablespaces: Things to keep in mind Never use them for system catalogs For RAW: No offsets available: set your raw
device to exactly the size you need No DB mirroring: mirror disk at OS level Cooked slightly more flexible, slightly slower When using multiple containers, make your
container sizes the same for load and data balancing!
Monitor with the “db2 list tablespaces show detail command”
Monitoring DMS Tablespaces db2 list tablespaces show detail Tablespace ID = 5 Name = BIGSPACE_1 Type = Database managed space Contents = Any data State = 0x0000 Detailed explanation: Normal Total pages = 4587520 Useable pages = 4587120 Used pages = 3137520 Free pages = 1449600 High water mark (pages) = 4474560 Page size (bytes) = 8192 Extent size (pages) = 240 Prefetch size (pages) = 240 Number of containers = 1
Creating an SMS Tablespace
CREATE temporary TABLESPACE TEMP2_8K IN DATABASE PARTITION GROUP IBMTEMPGROUP PAGESIZE 8192 MANAGED BY SYSTEM
USING ('/temp1_jfs2/tmp1_1') on nodes(1)
USING ('/temp2_jfs2/tmp2_1') on nodes(2)USING ('/temp3_jfs2/tmp3_1') on nodes(3)USING ('/temp4_jfs2/tmp4_1') on nodes(4) EXTENTSIZE 24 PREFETCHSIZE 72 BUFFERPOOL TEMP_8K OVERHEAD 12.500000 TRANSFERRATE 0.300000
SMS Tablespaces: Things to keep in mind Slowest Ideal for system catalogs Ideal for tempspace Easy to set up, minimal planning as they
Expand and Contract as required Cannot expand or add containers Monitor by watching the filespace fill and
empty
Monitoring SMS Tablespaces db2 list tablespaces show detail – always listed
as full, so watch file system too Tablespace ID = 9
Name = TTMP_8K Type = System managed space Contents = System Temporary data State = 0x0000 Detailed explanation: Normal Total pages = 18689 Useable pages = 18689 Used pages = 18689 Free pages = Not applicable High water mark (pages) = Not applicable Page size (bytes) = 8192 Extent size (pages) = 240 Prefetch size (pages) = 240 Number of containers = 1
Some Critical Notes on TablespacesSome parameters not seen in Informix:EXTENT SIZE – The extent size for all tables
in this tablespacePREFETCH SIZE – Pages grabbed at a timeBUFFERPOOL – name of the bufferpool the
tablespace will use. Must exist before table can be created, can be changed
OVERHEAD, TRANSFERRATE – Indicators of the speed of the disk the tablespace uses. Affects the optimizer
From Tablespaces to Memory Before you can create tablespaces, you
will need bufferpools with the same page size to dedicate them to
Can just use the default: IBMDEFAULTBP Can create specific buffers later, and
change with the “alter tablespace” command
Can never change the page size of an existing tablespace
Differences in MemoryINFORMIX BUFFERS SHMVIRTSIZE SHMTOTAL DS_TOTAL_MEMORY Log, backup buffers,
etc.(Resident, Virtual and
Message)
DB2 BUFFPAGE Custom
Bufferpools SHEAPTHRES SORTHEAP Lots of log, backup
and other little buffers
DB2 Bufferpool Basics Comes with a default IBMDEFAULTBP
Can create different buffer pools, with different page sizes, for different tablespaces and data
IBM doesn’t recommend using more than 2 different page sizes
Created in the database you are currently connected to
Creating Bufferpools This creates an 8K BufferpoolCREATE BUFFERPOOL M2_8K SIZE 175000 PAGESIZE 8192 NOT EXTENDED STORAGE;
In a Multi-Partition install, it is created across all partitions
Total size will be: SIZE * ( number of LPs)
Some BUFFERPOOL Recommendations Expand the default BUFFER with the alter
bufferpool command First try 1 big buffer for all your
tablespaces…this will probably be fine Experiment with the following:
Create small bufferpools for reference tables If you have a small number of large, busy
tables, create bufferpools for each Try creating a separate bufferpool for
tempspace
Let’s git it on!
Now that we know what Bufferpools, Tablespaces and Tables we need…let’s install and configure DB2!
But there’s a few things we’ll want to do first…
Layout Disk for Binaries and System Catalogs Create a filesystem directory
structure to install the binaries Create a filesystem to contain the
system catalogs (the database) Keep them separate from disk you
plan to put data on DB2 has no internal DB mirroring:
use OS mirroring
Layout Disk For Tablespaces
DB2 has 3 types of tablespaces, with different disk requirements
System Managed Space – Requires a filesystem directory structure for each path
DMS Raw – Requires raw devices for each container
DMS Cooked – Requires a filesystem directory structure to create containers in
Know when to use which, and why!
Differences in Install and Initial Configuration
INFORMIX Onconfig
Sqlhosts Informix.rc
DB2 Database Manager
Configuration (DBM Config)
Database Config (DB Config)
.rhosts Db2set
Install DB2 Binaries Very similar to Informix install:
RTFM! (Read the fine Manual) For DB2 Multi-Partition Installs:
requires that binaries be installed on each PHYSICAL node
Multi-Partition also requires creation of the db2nodes.cfg file before startup
Example db2nodes.cfg file Located in $db2home/sqllib Per P690 Red Book: 1 LP per CPU – I think
this is excessive.3 Columns: Absolute LP number, Name of
Physical Node, Number on Physical Node1 dbserver1 02 dbserver1 13 dbserver2 04 dbserver2 1
Starting DB2
As the database owner, just run:db2start
Setting up the DBM Config 1 per instance db2 get dbm cfg (for current settings) Cannot change with editor To Update:
db2 update dbm cfg using <param> <value> Changes affects the instance, and
therefore all databases in the instance Some changes take effect immediately,
most require a db2stop and db2start
DBM Config Parameters DFTDBPATH INTRA_PARALLEL SHEAPTHRES MONITOR SWITCHES (Buffer Pool,
Lock, Sort, Statement,Table, Timestamp, Unit of Work and the killer Health Monitor)
SVCENAME Backup, restore and audit buffers
Creating a DatabaseINFORMIX Location defaults
to rootspace (defined in config)
Put in dbspace Dbspace must
exist Raw space for best
performance
DB2 Location defaults
to DFLTDBPATH in DBM CFG
Put in OS path Path must exist System Managed
Space for best performance
Create Database Script
create database nhl_mart on /db2ins07/db2ese
catalog tablespace managed by system using ('/nhl_mart/syscat/nhl_sys');
DB Config One per database Cannot change with editor db2 get db cfg for <dbname> To update on a single partition server:
db2 update db cfg for <dbname> using <param> <value>
To update on a multi partition server: db2_all db2 update db cfg for <dbname>
using <param> <value>
DB Config Parameters BUFFPAGE – default bufferpool SORTHEAP – AVG_APPLS LOGFILSIZE, LOGPRIMARY,
LOGSECOND and NEWLOGPATH DFT_QUERYOPT – 1-9 LOGBUFSZ
Extra Step for Multi-Partition SetupIf doing a multi-partition install, you will
want to setup Partition Groups…since you probably don’t need all your data spread across every node!
CREATE DATABASE PARTITION GROUP "BIG_PART" ON DBPARTITIONNUMS
(1,2,3,4);CREATE DATABASE PARTITION GROUP "REF_PART" ON DBPARTITIONNUMS
(1);
Setting Up Logs For performance, recommend
setting up all logs as LOGPRIMARY Try to place logs on disk not used for
other activities. Set a new path with the NEWLOGPATH param, then bounce engine
Circular logging is a new feature
SHEAPTHRES: Major DB2 Memory Considerations
1. Do you do a lot sorting in this instance?…this database?
2. Do you anticipate (or observe) large overflows to tempspace?
3. Are you frequently reading large volumes of data from 2 or more tables?
If you answer YES to these questions, you may need SHEAPTHRES: SORT MEMORY
What is SORT HEAP? Individual rows are written to BUFFERS in
each database All sorts are done in a memory pool called
the Sort Heap SHEAPTHRES -a DBM parameter used to
set an instance wide max sort heap SORTHEAP – A DB parameter used by
each database to determines how much Sort Heap a single query can use within that database
SHEAPTHRES / SORT HEAP recommendations
Make sure SHEAPTHRES + BUFFERPOOLS is less than system memory
Start small – adding to SHEAPTHRES will require a reduction of BUFFERPOOLS
Capture SQL and monitor queries to gauge SORT OVERFLOWS
Set the SORTHEAP to fit evenly into SHEAPTHRES
When the SORTHEAP overflows to temp buffers, it writes the entire SORTHEAP. So, a large SORTHEAP may actually hurt performance!
Some Basic Monitoring To get any useful information, you
must turn on the Monitor Switches in the DBM CFG
Use “db2 list applications” to get the Appl. Handle number
Use “db2 get snapshot for application <Appl. Handle number>” for all information about that query
Some Get Snapshot Output
The output is much too extensive to review entirely, but here’s some interesting stuff that’s in it:
Dynamic SQL statement text Sort Overflows Rows Read, Rows Written Bufferpool Data Logical Reads
Some Cool Tools Materialized Query Tables: MQTs Index Advisor: db2advis Db2shema - db2look GETDISTRIB –Checking your Data
Distribution
What’s an MQT A Materialized Query Table is like a
summary table that is automatically referenced
Can be costly to build in terms of processing time and disk
If designed properly, can significantly reduce processing time on many reports by effectively having the results already processed.
Example MQTCREATE TABLE CORP.MQT_SALES AS ( SELECT STORE_NO, EMPNO, CUSTNO,
SUM(SALE_PRICE_RAW) as sale_price_raw,
SUM(COMMISSIONS) as commissions_paid_tot,
SUM(COST_OF_GOODS) as cost_of_goods_raw,
SUM(SALES_TAX) as sales_tax_tot
FROM CORP.SALES GROUP BY STORE_NO, EMPNO, CUSTNO)
data initially deferred refresh immediate ENABLE QUERY OPTIMIZATION
MAINTAINED BY SYSTEM
partitioning key (store_no) in bigspace_2 not logged
initially;
commit;
update command options using c off;
alter table CORP.MQT_SALES activate not logged initially;
REFRESH TABLE M2ADM.MQT_SALES NOT INCREMENTAL;
Defining Indexes with DB2 Advis
Use the DB2 Advis utility to analyze SQL statements for indexes
First capture a SQL statement that is exhibiting poor performance
Write it to file, say trouble.sql Run db2advis –d <dbname> -i <filename> -
o <output file>Example:db2advis –d testdb –i trouble.sql –o fix.out
DB2 Advis Output Will output an estimate (in timerons)
to run the query with and without the recommended indexes
Will output indexes (if any will help) Remember to add ALLOW REVERSE
SCANS to the create index statements!
DB2LOOK Use the DB2LOOK tool to output a
schema, or physical layout To get all options:
db2look ? The following would output all the
DDL needed to recreate the test database to a file called test.ddl
db2look –d test –e –l –o test.ddl
GETDISTRIB – Check distribution of a table
Use the GETDISTRIB from the db2 prompt to output the distribution of the data in a table
Syntax: getdistrib <tablename> <field>Example: getdistrib employee empnoReturns: 1) Partition Number 2) Rows1 2 ----------- ----------- 1 151967 2 138988 3 193551 4 162090
What are We Going to Do About All This Code?? Application code can be converted
to DB2 The question is:
how to convert how long will it take how will performance be after
conversion
What are We Going to Do About All This Code??
You will hear: SQL is SQL Just Point the Application at DB2 Just run the code through the
conversion tool To estimate:
Id all the code that will need to change (joins, group by, external table, truncate, etc) build an estimate, then at least double it !
Some Things We Learned - Support
Make friends with DB2 Developers in Toronto because the DB2 help desk does not answer SQL questions
DB2 SQL assistance is available for $
Informix Help Desk Does answer SQL questions
Some Things We Learned – Documentation
DB2 documentation is on par or better than Informix documentation (and Informix documentation is pretty good!)
Improvements to the documentation are in the works (adding examples)
Look at IBM.com, DB2 Technical Support, Product Manuals
The manuals we use most: SQL reference Volumes 1 and 2 Data Movement Utilities Guide and Reference
Some Things We Learned – Monitoring
Informix “onstat” commands make for easy monitoring
While monitoring tools are available in DB2, they can be awkward
Onstat type monitoring commands are on
the list to be added to DB2 in a future release
Some Things We Learned – Monitoring
Determine which processes are running: INFORMIX: Onstat –g ses/sql/act/athDB2: list applications show detail
View a specific process: INFORMIX: onstat –g ses <PID>DB2: get snapshot for application agentid <PID>
Kill a process: INFORMIX: onmode –z <PID>DB2: force application ‘(PID)’ or force application all
Some Things We Learned – Monitoring
View the database configuration: INFORMIX: onstat –c DB2: get database configuration and/or get
database managers configuration (get db cfg / get db mgr cfg)
View available tablespaces: INFORMIX: onstat –d/-D/-t/-T DB2: list tablespace show detail
Interactive Access
DBACCESS – Psuedo GUI, Menu bar driven DB2 CLP (command line processor) – A little
clumsy, but adequate. More like sybase or oracle interface
Getting Help Help dbaccess cntl-w Help ? CLP Command
Connecting Db2 initially requires an explicit connect Informix implicitly connects when using dbaccess
DB2CLP
Several ways to execute commands db2 <command> Example: db2 connect to mydb
You can also use interactive modedb2 –t
Connect to mydb;
Select col1, col2
From mytable;
Quit;
DB2CLP
You can execute OS commands within DB2 CLP
! Cp file1 file2
Get a list of databases:List active databases;
Get a list of columns:List tables [for schema <schemaname>;
Get the layout of a table:Describe table <schemaname>.<tablename>;
Calling from ksh Script
Dbaccess [dbname] <<EOF > stdout 2>stderror
Select bla bla bla;EOF Db2 –tvl <logfilename> <<EOF >Connect to [dbname];Select bla bla blaEOF
A few little things…
Default Permissions Informix: Public has permissions by default DB2: public does not
Updating Statistics (different syntax)Runstats on <schema>.<table> with distribution
And indexes all shrlevel change;
Code Comments DB2 does support the dash dash for comments However, they need to start in column #1 of a line
-- This works as a comment
somecol char(3) -- this does not
A few little things…
Don’t use double quotes in DB2 !Select * from tabname where name = ‘Bob’
DB2 does not support Directives
Datatypes
DB2 does not support implicit casting Explicitly cast all data types in
expressions Example:Create table bob.tabname (col1 integer,col2 char(10),col3
char(3))…
Insert into tabname values (null, ‘bob’, null) --informix
Insert into tabname values (cast(null as integer), ‘bob’, cast(null as char))
Limiting Number of Rows Returned/Optimize forNumber of Rows
Informix: Select first 100 ssn from people;
DB2: Select ssn from people Fetch first 100 rows only;
Optimize for a particular number of rows (db2 only)
Db2: Select ssn from people Optimize for 20 rows;
Join Syntax
DB2 Outer join syntax is different than Informix
DB2 is reportedly ANSI standard and Informix is not
Join Syntax
INFORMIX: Select a.name, a.employ_num, b.program, c.ed_level From
employee a, training b, OUTER education c Where a.employ_num = b.employ_num and
a.employ_num = c.employ_num and b.program = ‘DB2101’
DB2: Select a.name, a.employ_num, b.program, c.ed_level
From employee a INNER JOIN training b on a.employ_num = b.employ_num LEFT OUTER JOIN education c on a.employ_num = c.employ_num
Where b.program = ‘DB2101’
Group by
Can’t use “number” syntax Group by 1,2,3….
Forced to make case statements, etc redundant
Group by - INFORMIX
Select gender, state_of_birth,
Case when age > 19 and age < 31 then ‘Young’
when age > 30 and age < 46 then ‘middle aged’
when age > 46 then ‘Up there’
End category
From employee
Group by 1,2,3
Group by – DB2
Select gender, state_of_birth,
Case when age > 19 and age < 31 then ‘Young’
when age > 30 and age < 46 then ‘middle aged’
when age > 46 then ‘Up there’
End case
From employee
Group by gender, state_of_birth,
Case when age > 19 and age < 31 then ‘Young’
when age > 30 and age < 46 then ‘middle aged’
when age > 46 then ‘Up there’
End case
Having
Syntax available in DB2 and not Informix
Look for duplicate keysselect * from people_table where ssn in
(select ssn from people_table
group by ssn having count(*) > 1 );
Alter Statements
Alter capabilities are limited in DB2 Can’t drop a column Can’t change a datatype for a column
We of course used the alter – drop in our Informix Code!
UnLogged Tables
Using Unlogged databases in Informix is straight forward
Using Unlogged tables in db2 version 7.2 is Awkward Temporary Dangerous Still Possible
Db2 version 8.1 is less disastrous Basic problem is auto rollback makes table
permanently unavailable, must recreate or restore
UnLogged Tables
When creating a table must specify that logging can be turned off
Create table bob.xyz
(Col1 char(2))
In tablespace123 index in indexspace456
Not logged initially; Must alter the table to temporarily turn logging off
Update command options using c off;
Alter table bob.xyz activate not logged initially;
Insert into bob.xyz …
Commit; If anything goes wrong, boom no useable table!
Utilities
DB2 has import, export, load utilities Load is fastest way to get data into table Load can handle various delimiters or no delimiters You can replace or insert (append) Terminate or restart Example:
Load from /pathname/filename
Of del modified by coldel| keepblanks anyorder
Messages messagefile.msg
Temp files path /large_directory
Replace into bob.xyz;
Utilities
Another load example (using cursor):Declare cursor mycursor
select …
load from mycursor of cursor
METHOD P (1,2,3,4,5…)
replace INTO bob.xyz NONRECOVERABLE;
Approx 25% faster than using “insert into tablename select from..”
Utilities
Another load example (mapping cols):load from strip.txt OF ASC
METHOD L (1 7,9 43,45 54,56 90,92 126,128 145,
147 148,150 160,268 277,336 336)
messages messagefile.msg
tempfiles path $WORKDIR
replace INTO bob.xyz NONRECOVERABLE;
Import is slow
Utilities
Export has several differences from dbexport By default numbers have a + and leading zeros Character data is enclosed by double quotes Character data is padded to full length Example:
Export to filename.out
Of del modified by coldel| decplusblank
Select date_provided, rtrim(record_id) from tabname;
Used sed to strip out quotes and leading zeros New parameters nochardel and stripLzeros
Utilities
Getting the ddl Informix: dbschemaDbschema –d databasename outputfilename.out
DB2: db2lookDb2look –d databasename –e > outputfilename.out
Both have many options Both have usage built in, just type
command
Error Messages
Both databases provide error messages from the command line INFORMIX: finderr –217
-217 Column column-name not found in any table in the query(or SLV is undefined).The name appears in the select list or WHERE clause of this query but is…
DB2: db2 ? SQL0203SQL0203NA reference to column "<name>" is ambiguous.
Explanation: The column "<name>" is used in the statement …
INFORMIX XPS (Version 8.x)
DB2 does not have the external table feature, must up import, export and load utilities
DB2 requires explicit indexes to perform adequately
DB2 does not have the join update/batch update feature (a subselect must be used)
DB2 does not support truncate command
Summary
Yes, you too can migrate to DB2!
