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OMS heap collisions <percentage>%, <number_of> collisons during <number_of> heap allocations / deallocations


This message can occur for SAP liveCache technology only.

Tasks that run in different threads attempt to request or release memory from the OMS heap in parallel. This increases the number of collisions.


User Response

Check whether the SAP liveCache database parameter OmsSubHeaps, which determines the number of OMS heap segments, has an appropriate value.

The risk of collisions rises with the number of processors used (MaxCPUs general database parameter). Check whether the SAP liveCache database can fulfill the requirements of the applications with fewer processors. If not, check whether the CPU on the computer is overloaded, and whether the SAP liveCache threads are blocked by other applications running on the computer. If this is the case, the SAP liveCache threads that contain user tasks should have received REAL TIME PRIORITY in the operating system. To avoid blocking other applications running on the same computer, the value of MaxCPUs must be at least one lower than the number of actual CPUs.


More Information

Relevant  DB-Analyzer Files
Helpful with ...
DBAN_CACHE_OCCUPANCY.csvCache load and occupancy (proportion of OMS, SQL, and history pages in the data cache)
DBAN_OMS_HEAP.csvInformation on the OMS heap (such as occupancy, current size, collisions) 
DBAN_CPU_UTILIZATION.csv Information about the system load: CPU usage in user and system mode 
SAP Note
Helpful with ...
1128916 - FAQ: SAP MaxDB/liveCache Heap-Management  Provides information about the memory usage of the SAP MaxDB/liveCache kernel process. 
Expert Sessions (Link to trainings)
Content / Helpful with ...
Documentation (Links) 
Database Administration in CCMS 
Monitoring OMS Versions
Database Administration
General Database Parameters 
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