Bookshelf v7.5: DB2set Parameters

Use the db2set command to set the parameters (for example, db2set DB2_RR_TO_RS = YES) referenced in Table 21.

Table 21. db2set Parameters
Parameter	Explanation	Setting
`DB2MEMDISCLAIM`	For AIX only. When set to YES, DB2 agents explicitly request that the database server disassociate the reserved paging space from freed memory. Affects how DB2 frees shared memory.	YES
`DB2MEMMAXFREE`	For AIX only. Max. amount of unused memory in bytes retained by DB2 processes. It affects how DB2 frees shared memory and causes DB2 to release memory as soon as the size of the DB2 agent goes above the listed value.	3000000
`DB2_HASH_JOIN`	Turns off hash joins in optimizer.	NO
`DB2_RR_TO_RS`	Improves DB2 performance with Siebel eBusiness Applications. Set to YES only in production environment servers.	YES
`DB2_MMAP_WRITE`	Recommended setting only; you should evaluate this setting for your particular configuration and environment.	OFF
`DB2_MMAP_READ`	Recommended setting only; you should evaluate this setting for your particular configuration and environment.	OFF
`DB2_CORRELATED_PREDICATES`	When set to YES, the optimizer is able to determine whether predicates in a query are related, which permits DB2 to calculate the filter factor more accurately.	YES
`DB2_INDEX_2BYTEVARLEN`	If you use DB2 v7, set this parameter to ON. Otherwise, you will not be able to create indexes with columns greater than 255 bytes. You do not need to set this parameter for DB2 v8 because DB2 v8 supports type-2 indexes.	ON
`DB2_PIPELINED_PLANS`	Tells the DB2 optimizer to favor pipeline execution plans—plans that are left deep and have no temporary result sets.	ON
`DB2_INTERESTING_KEYS`	Limits the number of execution plans generated by the DB2 optimizer.	ON
`DB2_PARALLEL_IO`	Useful when using RAID devices. For more information, see your DB2 vendor documentation.	ON
`DB2_STRIPED_CONTAINERS`	Useful when using RAID devices. For more information, see your DB2 vendor documentation.	ON
`EXTSHM`	This parameter only applies to AIX. Use this parameter only if you need to run 32-bit applications where more than 11 shared memory segments per process are required and you need shared memory of the shmat variety. Shmat is PowerPC hardware segment related, therefore memory is more efficiently managed and protected in all segments.For more information, see EXTSHM.	ON
`DB2ENVLIST`	When starting a DB2 UDB server and running `EXTSHM`, `EXTSHM` must be part of the DB2 environment. This parameter must be set when the database is created.	EXTSHM
`DB2_NO_PKG_LOCK`	To bind the Siebel package with `siebbind`, this package must be off.	OFF

EXTSHM

This parameter must be set when both the DB2 UDB and DB2 UDB EEE databases are created, and included in the script that starts them.

You should also include this parameter in the script that starts the DB2 client.

Additionally, this line must appear in the sqllib/db2profile for the DB2 UDB EEE server.

NOTE: After changing any of these settings, you must perform a db2stop/db2start to implement the changes in your DB2 database.