Db2 pureScale registry variables

There are several registry variables available for use specifically with Db2 pureScale.

DB2_DATABASE_CF_MEMORY
  • Operating system: All
  • Default: AUTO, Values: -1, or 0 to 100, or AUTO
  • Type: Float
  • When DB2_DATABASE_CF_MEMORY is unset or set to AUTO, CF memory is self-tuned for all databases that have these database configuration parameters set to AUTOMATIC: cf_gbp_sz, cf_lock_sz, and cf_sca_sz. DB2_DATABASE_CF_MEMORY can be changed dynamically, and a database manager restart is not required.
  • DB2_DATABASE_CF_MEMORY is used to indicate the proportion of total CF memory (CF_MEM_SZ) assigned to each database that has database configuration parameter cf_db_mem_sz set to AUTOMATIC. Any database that has cf_db_mem_sz set to a specific value ignores this registry variable.
  • For all databases to have an equal share of the CF memory resources when more that 100 databases are active, the DB2_DATABASE_CF_MEMORY registry variable must use values less than 1. For example, if there are 200 active databases, each with an equal share of the CF memory, this registry variable must be set to 0.5.
  • Use of the DB2_DATABASE_CF_MEMORY registry variable must be coordinated with the cf_db_mem_sz and numdb configuration parameters. For more information, see Db2 pureScale CF memory parameter configuration.
DB2_MCR_RECOVERY_PARALLELISM_CAP
  • Operating system: All
  • In a multiple database environment, if member crash recovery (MCR) is required, the number of databases recovered in parallel on each member is set by the value of the numdb configuration parameter or the DB2_MCR_RECOVERY_PARALLELISM_CAP registry variable, whichever value is smaller.
DB2_SD_ALLOW_SLOW_NETWORK
  • Operating system: All
  • Default: OFF, Values: ON, OFF
  • This variable allows an Ethernet card that is less than 10GE to use the TCP option of the cf_transport_method configuration parameter.
  • This lower transfer rate Ethernet card limits performance.
DB2_AVOID_TIMEOUT_ON_EHL_LOCKS
  • Operating system: All
  • Default: NO, Values: YES, NO
  • For Db2 pureScale environments, this registry variable indicates whether the application should wait for a table to exit the NOT_SHARED state of the Explicit hierarchical locking feature. If set to YES, no lock timeout error (SQL0911N) is generated due the need to wait for table to exit the NOT_SHARED state.
  • Changes to this registry variable take effect immediately, without recycling the instance or the database.
DB2_CF_SERVER_CACHE_STOCLASS_NUM_QE_QUEUES
  • Operating system: All
  • Default: 1, Values: 1to 112 inclusive
  • For Db2 pureScale environments, this registry variable sets the number of QE queues. The variable configures one QE queue by default. Contentions may occur on Db2 pureScale clusters that run workloads with high concurrency and read-activity rates, resulting in reduced CPU usage on the CF hosts as well as a drop in performance. On systems with these contentions, set the registry variable on systems to be double the CF_NUM_WORKERS value, and no higher than 112. This registry variable only applies to Db2 11.5.9 and later.

  • Changes to this registry variable take effect at instance start.