Ingres Version 6.4 An Overview of the Architecture

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Ingres Version 6.4An Overview of the Architecture

• Presented by
• Quest Software

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Ingres 6.4 - An Overview

• Client / Server Architecture
• Components
• Locking I/O
• Server Internals
• Query Processing

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Client - Server Architecture
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Client - Server Architecture

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

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Name Server

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

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Name Server
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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 ?

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Name Server - Ingres /Net
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DBMS Server

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

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Components
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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

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Logging and Recovery (cont)
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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

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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

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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

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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 !

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Components
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Locking

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

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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

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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

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Server Internals
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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)

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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)

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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 users front end
  program !

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Conclusions

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