Db2 pureScale Feature cluster caching facility (CF) configuration

In a Db2 pureScale environment, the cluster caching facility, also known as CF, is used to facilitate global locking and buffer pool management. CF configuration is integrated into Db2 infrastructure and managed by Db2 configuration interfaces.

The CF configuration has a unique set of configuration parameters to optimize a Db2 pureScale environment.

Configuration parameters for the CF are categorized as either:
  • CF server configuration parameters: configured as Db2 database manager configuration parameters
  • CF structure configuration parameters: configured as Db2 database configuration parameters
Default settings are applied to the configuration file when a Db2 pureScale Feature instance or a database is created.

Cluster caching facility configuration

The CF server configuration information is maintained as part of the Db2 database manager configuration information. As such, the CF server is configured in the same way the database manager is configured using Db2 configuration interfaces. The Db2 Command Line Processor (CLP) or the configuration APIs can be used to display and update configurable CF server information.

These configuration parameters support the CF server:
  • cf_diaglevel
  • cf_diagpath
  • cf_mem_sz
  • cf_num_conns
  • cf_num_workers

Cluster caching facility structure configuration

CF structure memory is maintained as part of Db2 database configuration information. CF structure parameters are configured in the same way Db2 database parameters are configured using the Db2 CLP or configuration APIs to display and update configurable CF structure.

These configuration parameters are added to support the CF structure:
  • cf_db_mem_sz
  • cf_gbp_sz
  • cf_lock_sz
  • cf_sca_sz

CF structures are created in the CF server for each database. During a call to CREATE DATABASE command, the Db2 configuration advisor also sets CF structure configuration parameters to their default value AUTOMATIC and computes the appropriate startup values for your Db2 pureScale instance.

Proper CF structure configuration is important to achieve optimal performance in a Db2 pureScale environment. The computed defaults for CF structures might not achieve optimal performance for your Db2 pureScale environment.

In a performance benchmark environment, manually tune the CF structure sizes to achieve the required level of performance. Also be aware that using table partitioning under Db2 pureScale incurs additional memory usage.

Configuration Advisor

The Db2 Configuration Advisor is invoked when creating a database to set a reasonable set of defaults for the database configuration based on the host environment such as the amount of memory and the number of processors.

The Db2 Configuration Advisor is enhanced with the Db2 pureScale Feature to compute the startup values for the CF structure configuration parameters. To ensure the best distribution of memory among these structures and to achieve reasonable performance standards for a Db2 pureScale instance, these parameters are computed based on the total CF memory size defined by cf_mem_sz:
  • cf_db_mem_sz,
  • cf_gbp_sz,
  • cf_lock_sz, and
  • cf_sca_sz.

High availability with two cluster caching facilities

You must set up two CF servers when running in a Highly Available (HA) CF environment. One CF acts as the primary server and the other as a backup or secondary CF server.

In this environment the primary CF server and the secondary CF server share the same host configuration.

For more information about structure duplex support in high availability environments, see Structure duplex support behavior with a secondary cluster caching facility.

In a Db2 pureScale environment where there are two CF servers, you can replace both cluster caching facilities using a rolling upgrade technique to maintain an environment that is highly available.

For more information about maintaining a high availability environment during CF replacement, see Replacing both cluster caching facilities.