Performance Tuning for Content Manager

226 Performance Tuning for Content Manager

Also watch LOCK_LIST_IN_USE (total lock list memory in use). If this element is

high (exceeds 50% of the defined LOCKLIST size), you might want to consider

increasing the size of the parameter. Note that the monitor element is reported in

bytes, but the LOCKLIST parameter is in 4-kilobyte pages.

To determine the maximum number of locks held by a given transaction, check

the LOCKS_HELD_TOP (maximum number of locks held) monitor element. The

monitor information is provided at a transaction level, not an application level.

The following steps help you determine the number of pages required for your

lock list:

1. Calculate a lower bound for the size of your lock list using one of the following

formulas, depending on your environment:

– (512 * x * MAXAPPLS) / 4096

– With connection concentrator enabled:

(512 * x * MAX_COORDAGENTS) / 4096

512 is an estimate of the average number of locks per application and x is the

number of bytes required for each lock against an object that has an existing

lock (36 bytes on 32-bit platforms, 56 bytes on 64-bit platforms).

2. Calculate an upper bound for the size of your lock list using the formula:

(512 * y * MAXAPPLS) / 4096

y is the number of bytes required for the first lock against an object: 72 bytes

on 32-bit platforms, 112 bytes on 64-bit platforms.

3. Estimate the amount of concurrency you will have against your data and

based on your expectations; choose an initial value for locklist that falls

between the upper and lower bounds, which you have calculated.

4. Using the database system monitor, tune the value of this parameter.

You might also want to increase LOCKLIST if MAXAPPLS is increased, or if the

applications being run perform infrequent commits.

You should consider performing a rebind after changing this parameter.

8.6.20 Application control heap size (APP_CTL_HEAP_SZ)

Impact

DB - Medium

Description

For partitioned databases, and for non-partitioned databases with

intra-parallelism enabled, this parameter specifies the average size of the shared

Chapter 8. Tuning DB2 for Content Manager 227

memory area allocated for an application. For non-partitioned databases where

intra-parallelism is disabled, this is the maximum private memory that will be

allocated for the heap. There is one application control heap per connection per

partition.

The application control heap is required primarily for sharing information between

agents working on behalf of the same request. Use of this heap is minimal for

non-partitioned databases when running queries with a degree of parallelism

equal to 1.

This heap is also used to store descriptor information for declared temporary

tables. The descriptor information for all declared temporary tables that have not

been explicitly dropped is kept in this heap’s memory and cannot be dropped

until the declared temporary table is dropped.

Default values (range)

128 (1 - 64,000) pages for database server with local and remote clients

64 (1 - 64,000) pages for database server with local clients, non-UNIX platforms

128 (1 - 64,000) pages for database server with local clients, UNIX platforms

256 (1 - 64,000) pages for partitioned database server with local and remote

clients

To update

Run the following DB2 command:

db2 update db cfg for <database name> using APP_CTL_HEAP_SZ <parameter

value>

Our recommendation

The Content Manager installation program changes this to 1000 for the Library

Server and 128 for the Resource Manager.

Use these default values. If you have memory constraints, reduce the value on

the Library Server database.