You can configure, on a per-server basis, the maximum memory size of the RLV store.
Prerequisites
- SAP Sybase IQ server has a simplex database.
Task
The size of the RLV store should be carefully chosen to avoid exceeding the physical
memory on the host. Therefore, consider:
- Physical memory available to the host
- Size of IQ main store and temporary buffer caches
- Size of IQ large memory pool
- Memory requirements of other applications running on the host
Choosing a value which is too small will result in extra merges. This may potentially
cause DMLs to fail if the frequency of the automated merge is too high.
- Use the -iqrlvmem boot parameter, to specify the maximum size of
the RLV store in Mb.
-iqrlvmem 8192
This specifies an RLV size of 8192 Mb.
Note: A DML which causes the size of the RLV store to exceed the configured memory
limit will immediately trigger an automatic merge. However, the
RV_MERGE_NODE_MEMSIZE node threshold will usually trigger the automated merge
before this limit is reached.
- (Optional) At runtime, change the size of the RLV store using the
sa_server_option.
sa_server_option 'RLV_memory_mb', 16384
This reconfigures the RLV store size to 16384 Mb.
Note: This size is a “soft” limit. It is possible for the RLV store to temporarily
exceed the configured memory. RLV store memory is normally freed by merge.
However merge itself requires memory. Therefore during merge the memory limit may
be temporarily exceeded. Furthermore, open transactions remain in the RLV store
(and thus use memory), even after the merge.