applheapsz - Application heap size configuration parameter

The applheapsz configuration parameter refers to the total amount of application memory that can be consumed by the entire application.

In versions of Db2® prior to Version 9.5, the applheapsz database configuration parameter referred to the amount of application memory each individual database agent working for that application could consume.

With Version 9.5, this database configuration parameter has a default value of AUTOMATIC, meaning that it increases as needed until either the appl_memory limit is reached, or the instance_memory limit is reached. For partitioned database environments, Concentrator, or SMP configurations, this means that the applheapsz value used in previous releases might need to be increased under similar workloads, unless the AUTOMATIC setting is used.

Configuration type

Database

Parameter type

Configurable online
Configurable by member in a Db2 pureScale® environment

Default [range]

32-bit platforms: Automatic [16 - 60 000]
64-bit platforms: Automatic [16 - 2 147 483 647]

Note: The default value is subject to change by the Db2 Configuration Advisor after initial database creation.

Unit of measure

Pages (4 KB)

When allocated

When an application associates with, or connects to, a database.

When freed

When the application disassociates or disconnects from the database.

Note: This parameter defines the maximum size of the application heap. One application heap is allocated per database application when the application first connects with the database. The heap is shared by all database agents working for that application. (In previous releases, each database agent allocated its own application heap.) Memory is allocated from the application heap as needed to process the application, up to the limit specified by this parameter. When set to AUTOMATIC, the application heap is allowed to grow as needed up to either the appl_memory limit for the database, or the instance_memory limit for the database partition. The entire application heap is freed when the application disconnects with the database.

The online changed value takes effect at an application connection boundary, that is, after it is changed dynamically, currently connected applications still use the old value, but all newly connected applications will use the new value.