Ingres Version 6.4Ingres Version 6.4An Overview of the An Overview of the

ArchitectureArchitecturePresented by

Quest Software

Ingres 6.4 - An OverviewIngres 6.4 - An Overview

• Client / Server Architecture• Components• Locking & I/O• Server Internals

– Query Processing

Client - Server ArchitectureClient - Server Architecture

Client - Server ArchitectureClient - Server Architecture

• User Image• Name Server• DBMS Server• Archiver• Recovery Process

Name ServerName Server

• isql dbname– image activated

– call Ingres General Communication Facility (GCF) routines

– opens connection to Name Server

Name ServerName Server

Name ServerName Server

• Uses “GCA” Protocol• Receives connection request from User

Image• Provides mailbox address to User• User Image Connects to DBMS• What about Ingres / Net ?

Name Server - Ingres /NetName Server - Ingres /Net

DBMS ServerDBMS Server

• The Ingres “engine”• Accepts incoming SQL• Processes it• Executes I/O on behalf of Users• Multi - threaded

ComponentsComponents

Logging and RecoveryLogging and Recovery

• DBMS Server– writes to memory log buffers

• Recovery Process– Reads from memory log buffers

– Writes to Physical Log File

– Returns “ok to complete” to Server

• DBMS Server– writes to the database

Logging and Recovery (cont)Logging and Recovery (cont)

Logging and Recovery (cont)Logging and Recovery (cont)

• “Circular” Log File• All transactions which update the

database are logged• Writes “Before Image” to log file• “Transaction Complete” stamp after

complete• Write to the log file BEFORE the

database

Group Commit / Fast CommitGroup Commit / Fast Commit

• Group Commit– Sever writes query “A” to log buffers

– Sever writes query “B” to same buffers

– All “commits” are written together

• Fast Commit– Server writes “forces” directly to Log File

– then writes to the database (Cached)

– Write-Behind threads write to the database

ArchivingArchiving

• Log File has periodic “Consistancy Points”

• Archiver reclaims space from the Log File

• Only extracts COMMITED transactions from the Log File

• Writes transactions to the Journals• Moves the End Of File marker forward

Archiving (cont)Archiving (cont)

• If there are Uncommitted Transactions in the Log File– Archiver Process cannot extract them

– Cannot move the EOF marker

– Log File Fills Up

– Chaos !

ComponentsComponents

LockingLocking

• Initiated by Server Process• Types

– Exclusive / Shared

• Levels– Page / Table / Database

• VMS Cluster– II_CSP talks to clusterwide lock manager

Locking (cont)Locking (cont)

• Locking Escallation can Occur when– MAXLOCKS exceeded

– Locks Per Transaction exceeded

– Ingres installation-wide resources low

• “Blocking Locks”– Cause Deadlock checking to start

I/O HandlingI/O Handling

• Unix has Synchronous I/O– call iislave processes to offload I/O

requests

– II_NUM_SLAVES

– how many ?

• VMS has Asynchronous I/O

Server InternalsServer Internals

Query Processing - Parsing Query Processing - Parsing

• Query arrives in Server Control Facility (SCF)

• Store Text in Query Storage Facility (QSF)

• Parse the Query (PSF)• Check the Relational Descriptions (RDF)• Check Query Modifications due to

Permits, Views etc. (QRYMOD)

Query Processing - PlanningQuery Processing - Planning

• Create a Parsed Query Tree in QSF• Optimiser (OPF) uses Query Tree &

Statistics to develop Query Plan• Store the Query Plan in QSF• Query Execution Facility validates table

descriptions (QEF)

Query Processing - ExecutionQuery Processing - Execution

• Access the actual files using the Data Manipulation Facility (DMF)

• DMF returns data to QEF• QEF returns data to SCF• SCF returns data to GCA

communications• Eventually ends up at the user’s front

end program !

ConclusionsConclusions

• Ingres DBMS is complex• Multiple Components• Handle with care !!!