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Guidelines for Setting DB2 UDB Database Manager Configuration Parameters


This topic is part of Configuring an IBM DB2 UDB Database for Siebel Applications.

You can set the database configuration parameters using the update database manager configuration command of the DB2 Command Line Processor or using the DB2 Control Center.

For more information on modifying these configuration parameters, see the IBM DB2 UDB technical documentation.

Table 7 describes DB2 UDB database manager configuration parameters that differ from the default settings. Set these parameters for each DB2 UDB instance. Use the configuration information in Table 7 for the listed parameters. For parameters not listed in this table, accept the default settings.

Table 7. DB2 UDB Database Manager Configuration Parameters
Parameter
Explanation
Setting/Comment

SHEAPTHRES

Sort heap threshold (4 KB)

200000

Deployments with 3,000 or more concurrent users and using over 5 GB of RAM can increase this to 300000.

DIR_CACHE

Directory cache support

YES

ASLHEAPSZ

Application support layer heap size

15

RQRIOBLK

Maximum requester I/O block size (bytes)

65535

MON_HEAP_SZ

Database monitor heap size (4 KB)

128 (minimum)

QUERY_HEAP_SZ

Query heap size (4 KB)

16384

KEEPFENCED

Keep Fenced process

YES

MAXAGENTS

Maximum number existing agents

20000 (minimum)

NUM_INITAGENTS

Initial number agents in pool

10

NUM_POOLAGENTS

Number of agents in the agent pool kept active at all times

80

MAX_COORDAGENTS

Maximum number coordinating agents

MAXAGENTS

INDEXREC

Index re-creation time

RESTART

INTRA_PARALLEL

Enable intra-partition parallelism

NO

INSTANCE_MEMORY

Amount of memory to be reserved for instance management

automatic

DB2set Parameters

Use the db2set command to set the parameters (for example, db2set DB2_HASH_JOIN = NO) referenced in Table 8.

Table 8. db2set Parameters
Parameter
Explanation
Setting

EXTSHM

(AIX only) Use this parameter only when you have the Siebel Database and the Siebel Server on the same AIX machine.

EXTSHM must be set when the DB2 UDB database is created and must be included in the script that starts it. The parameter also must appear in the sqllib/db2profile file for the DB2 UDB server.

Include this parameter in the script that starts the DB2 client.

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

ON

DB2ENVLIST

(AIX only) 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

DB2MEMDISCLAIM

(AIX only) When set to YES, DB2 disclaims some or all freed memory, depending on the value of DB2MEMMAXFREE.

YES

DB2MEMMAXFREE

(AIX only) Maximum amount of unused memory in bytes retained by DB2 processes. Unset this parameter to use DB2 UDB's default memory management settings.

unset this parameter

DB2_MMAP_READ

(AIX only) Recommended setting only; evaluate this setting for your particular configuration and environment.

OFF

DB2_MMAP_WRITE

(AIX only) Recommended setting only; 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_HASH_JOIN

When set to NO, turns off hash joins in the optimizer, as may be generally suitable for OLTP deployments.

NO

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.

*

DB2_PIPELINED_PLANS

Tells the DB2 optimizer to favor pipeline execution plans—plans that are left deep and have no temporary result sets.

MODE2

DB2_REDUCED_OPTIMIZATION

Controls optimization techniques used at specific optimization levels.

IXOROFNR

DB2_STRIPED_CONTAINERS

Useful when using RAID devices. For more information, see your DB2 vendor documentation.

ON

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