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Disable Auto Merges Scenario in SAP HANA Delta Merge

Romil Tripathi || 27 Mar 2015 5:41 pm || 1

Hello,

In which scenarios can SAP HANA Delta Merges be useful to reduce or disable auto merges?

Thanks in advance.


Comments

  • 14 Apr 2015 1:50 pm Helpful Answer

    Disabling auto merges is mainly useful in scenarios of mass changes, e.g. data loads (many INSERTs) or archiving (many DELETEs). Several standard functionalities already work in this way:

    • In BW environments auto merges explicitly disabled for certain table types in order to speed up operations like data loads. BW relies on smart merges triggered on application side.
    • Migration tools disable auto merges or set the auto_merge_decision_func to values that result in less auto merges.

    The effect of reducing or disabling auto merges depends on several factors like the COMMIT frequency and the actual DML activities. Furthermore it is a trade-off between performance and memory consumption. The fewer merges are done, the larger is the memory requirement. Therefore a general rule of thumb is not available and you have to test the different options if you perform time-critical mass changes.