Ingres Version 6.4 An Overview of the Architecture Presented by Quest Software

Ingres An Overview Client / Server Architecture Components Locking & I/O Server Internals –Query Processing

Client - Server Architecture

User Image Name Server DBMS Server Archiver Recovery Process

Name Server isql dbname –image activated –call Ingres General Communication Facility (GCF) routines –opens connection to Name Server

Name 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 /Net

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

Components

Logging 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)

“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 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

Archiving 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) If there are Uncommitted Transactions in the Log File –Archiver Process cannot extract them –Cannot move the EOF marker –Log File Fills Up –Chaos !

Components

Locking Initiated by Server Process Types –Exclusive / Shared Levels –Page / Table / Database VMS Cluster –II_CSP talks to clusterwide lock manager

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 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 Internals

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 - 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 - 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 !

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