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Weekly Tips from DB2 Experts: How to tune FMP memory

Technical Blog Post


Abstract

Weekly Tips from DB2 Experts: How to tune FMP memory

Body

FMP memory can be configured with the help of  the registry variable DB2_FMP_COMM_HEAPSZ and the  database manager configuration parameter aslheapsz.

The default DB2_FMP_COMM_HEAPSZ is 256 MB on AIX and 20 MB on other OS

memory used by each FMP process = 2 *  ASLHEAPSZ

If the active fenced routines exceed this limit then we see the following message in the db2diag.log

MESSAGE : Insufficient memory available for IPC communication with the db2fmp
          process. Use the DB2_FMP_COMM_HEAPSZ registry variable to adjust the
          amount of memory available for fenced routines.

 

Example
  

FMP processes that would be active on the database = 500
ASLHEAPSZ set to 128 4K pages = 512 KB
Memory taken by each FMP process = 2 * ASLHEAPSZ = 2 * 512 = 1 MB
To accommodate 500 FMP processes we need 500 MB of FMP memory

db2 set DB2_FMP_COMM_HEAPSZ = 128000 (4K pages)
 

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ibm13287019