Some registry and environment variables have changed

Details

New variables

These environment and registry variables are new in Version 10.1:

Table 1. Environment and Registry variables added

Registry variable	Description
DB2_ALLOW_WLB_WITH_SEQUENCES	You can use this registry variable to control whether applications that access sequences are allowed to participate in workload balancing.
DB2_BCKP_INCLUDE_LOGS_WARNING	Starting in Version 10.1 Fix Pack 2, you can use this new variable to specify that online backups can succeed even if they fail to include all of the necessary log files.
DB2_BCKP_PAGE_VERIFICATION	Starting in Version 10.1 Fix Pack 2, you can use this new variable to specify that DMS and AS page validation occurs during a backup.
DB2_BACKUP_USE_DIO	You can use this registry variable to have a backup image file directly written to disk, bypassing the file cache, potentially leading to better memory utilization on Linux platforms. This registry variable is available in V10.1 Fix Pack 1 and later fix packs.
DB2_HISTORY_FILTER	You can use this variable to specify operations that are not to modify the history file, thereby reducing potential contention on the history file This registry variable is available in V10.1 Fix Pack 1 and later fix packs.
DB2_INDEX_PCTFREE_DEFAULT	You can use this registry variable to specify what percentage of each index page to leave as free space when building the index.
DB2_MAX_GLOBAL_SNAPSHOT_SIZE	Starting in Version 10.1 Fix Pack 2, you can use this new variable to specify the maximum size a snapshot or snapshot estimate can be, thereby preventing large global snapshots from causing memory usage spikes.
DB2_MCR_RECOVERY_PARALLELISM_CAP	You can use this registry variable to limit how many active databases are recovered in parallel on a member during member crash recovery. You can use this variable only in a DB2® pureScale® environment.
DB2_SAS_SETTINGS	This DB2 registry variable is the primary point of configuration for in-database analytics with the SAS embedded process.
DB2_SMP_INDEX_CREATE	Introduced in Version 10 Fix Pack 4, this DB2 registry variable overrides the default number of agents used to scan and sort the index data when building or rebuilding an index.
DB2TMPDIR	This variable is used to specify a path for the temporary files directory.
DB2_XSLT_ALLOWED_PATH	You can use this registry variable to control whether the DB2 instance refers to external entities defined inside of an XSLT stylesheet.

New values in existing registry variables

The following table shows the registry variables that have new values for Version 10.1 instances:

Table 2. Registry variables with new values

Registry variable	New values
DB2_PMODEL_SETTINGS	You can now use this variable's new SRVLST_EQUAL_WEIGHT option to override the default behavior in which member weights are computed based on load, and have non-zero member weights in the server list always be identical.

Changed behaviors

The following table describe the changes to registry variables when you create or upgrade to a Version 10.1 instance:

Table 3. Registry variables with changed behaviors

Registry variable	Changed behavior
DB2_ANTIJOIN	Starting in Version 10.1 Fix Pack 1, the default for this variable in non-ESE environments is EXTEND, meaning that the optimizer searches for opportunities to transform both NOT IN and NOT EXISTS subqueries into anti-joins.
DB2BPVARS	The NUMPREFETCHQUEUES and the PREFETCHQUEUESIZE option of this variable have been discontinued as optimization improvements render these options obsolete. The DB2BPVARS registry variable is still deprecated.
DB2_EXTENDED_OPTIMIZATION	The ENHANCED_MULTIPLE_DISTINCT setting has been deprecated and might be removed in a future release. Version 10.1 includes enhancements to improve the performance of multiple distinct queries. These enhancements are supported in all environments including partitioned database and DB2 pureScale environments. These enhancements are enabled by default in newly created databases and upgraded databases where this registry variable is not set to ENHANCED_MULTIPLE_DISTINCT. If you keep this setting, the previous release behavior is maintained. You should remove this setting to make the new enhancements available and benefit from better query performance.
DB2_NO_FORK_CHECK	This registry variable is no longer deprecated. Continue to use this variable to have the DB2 runtime client minimize checks to determine if the current process is a result of a fork call.
DB2NTNOCACHE	This registry variable is no longer deprecated. Continue to use this variable to override the undocumented 192 MB limit for the cache.

Resolution

Take advantage of enhanced functionality or new features by adopting new functionality through the use of new registry variables or new values for existing registry variables.

For new registry variables or changes to existing registry variables that result in DB2 server behavior changes, adjust your existing applications or scrips.

Review the list of deprecated and discontinued registry variables to learn about additional changes that might impact your applications and scripts and determine whether you have to adjust them or not.