DB2 Architecture

DB2 Architecture

• On the client side, either local or remote applications, or both, are linked with the DB2 Database
• Local clients communicate using shared memory and semaphores. Remote clients use a protocol such as Named Pipes, TCP/IP, Net BIOS, etc.

Server Side :

• server side, activity is controlled by engine dispatchable units (EDUs). 
• In the above figure EDUs are shown as circles or groups of circles.
• DB2 agents are the most common type of EDUs. These agents perform most of the SQL processing on behalf of applications. 
• Prefetchers and page cleaners are other common EDUs. 
• A set of sub-agents might be assigned to process the client application requests. 
• Multiple sub-agents can be assigned if the machine where the server resides has multiple processors or is part of a partitioned database.

1. Buffer pools are areas of database server memory where database pages of user table data, index data, and catalog data are temporarily moved and can be modified.
2. Buffer pools are a key determinant of database performance because data can be accessed much faster from memory than from disk.

• Prefetchers retrieve data from disk and move it into the buffer pool before applications need the data.
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• Page cleaners move data from the buffer pool back out to disk. Page cleaners are background EDUs that are independent of the application agents. They look for pages from the buffer pool that are no longer needed and write the pages to disk.

These are the perameters to set the Prefetchers & Pagecleaners

NUM_IOSERVERS  ===> DB CFG

MINCOMMIT   ==>  DB CFG

NUM_IOCLEANERS ==> DB CFG