Collision rate 

<region_name>: collision rate (<percentage>%), <number of> collisions, <number of> accesses on region <region_ID>

Explanation

The rate of lock collisions is very high.

Tasks that run in different threads are attempting to access a global region in parallel. The synchronization that enables this often leads to collisions.

One exception to this in liveCache instances are high collision rates in the regions ( <region-name>) OMSVDIR and CNSTVIEW. This is normal for certain actions, such as a simultaneous CIF queue transfer.

User Response

You need to act if the collision rate rises above 10%. Generally, the risk of collisions rises with the number of processors used (database parameter MAXCPU). Check, therefore, whether the database system can fulfill the needs of the applications with fewer CPUs in multiprocessor systems.

If high collision rates occur in multiprocessor central systems (database system and application run on the same server), check whether the CPU on the server is overloaded, and whether the database threads are blocked by other applications. In this case, the database threads that contain user tasks; should have REAL TIME PRIORITY in the operating system. However, at the same time, the value of MAXCPU must be at least one lower than the number of real CPUs, to avoid operating system blocks.

Additional Actions

If the high collision rates occur in the regions DATAn, SPLITn or TREEn, then increase the values of the database parameters _DATA_CACHE_RGNS, _TREE_RGNS, and CACHE_SIZE.

If the high collision rates occur in the regions TRACE or BUFWRTR, then activate the database trace temporarily for troubleshooting only.