Page 99 - DCAP408_WEB_PROGRAMMING

Unit 6: Memory Management (II)

Notes
Figure 6.1: Types of Memory Utilized by the Database Manager

Memory is assigned for every instance of the database manager when the following events take
place:
 When the database manager is started: Database manager global shared memory is assigned
and remains assigned until the database manager is stopped. This area includes information
that the database manager utilizes to handle activity across all database connections.
Instance shared memory can be handled by the instance_memory configuration parameter.
By default, this parameter is fixed to automatic in order that DB2 computes the amount of
memory assigned for the instance.
 When a database is activated or linked to for the first time: Database global memory is
assigned. Database global memory is utilized across all applications that attach to the
database. The size of the database global memory is stated by the database_memory
configuration parameter. By default, this parameter is fixed to automatic in order that DB2
computes the quantity of memory assigned for the database. You can fix database_memory
to assign more memory than is required originally so that the additional memory can be
dynamically distributed afterwards.
 Even though the total quantity of database global memory cannot be increased or
decreased while the database is active, memory for areas enclosed in database global
memory can be accustomed.

Example: The following memory areas can be dynamically accustomed to decrease
memory allocated to one area and augment memory in another area.
 Buffer pools (using the ALTER BUFFERPOOL DDL statement)
 Database heap (including log buffers)
 Utility heap

 Package cache
 Catalog cache
 Lock list
In the surroundings in which the database manager intra-partition parallelism configuration
parameter (intra_parallel) is enabled, or in the surroundings in which the connection concentrator
is enabled, the shared sort heap is also assigned as piece of the database global memory.

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