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SAP HANA - Memory Usage / Activating the Trace

Hello together,

I have two questions about the Memory Usage in SAP HANA, as it is described on Page 13-14 in SAP HANA Developer's Guide for the SQL Function Fuzzy Search - SAP HANA Appliance Software SPS 04.

1) When I fire off the following SQL-Statement in the HANA-Cloud (30 days trial), I get no result:

I would like to check to additional memory consumption by adding a fuzzy-search-index in several columns.

SELECT * FROM sys.m_heap_memory WHERE category LIKE '%FuzzySearch%'

-> Why do I get no result?

2) Do I have to activate the TRACE in SAP HANA Studio, to check the Memory Usage by fireing off the above named SQL-Statement?

Thank you very much for helping.

Best Regards,

Michael

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  • Posted on Dec 17, 2012 at 08:18 AM

    Hello Michael,

    I just tried this out with a simple example and as I suspected, the memory pool allocation is dynamic here as well.

    Only after actually performing the first fuzzy search (SELECT ... CONTAINS ( ... ) ) the pool appeared in the M_HEAP_MEMORY view.

    Concerning the second question: not too sure what you're looking for here.

    Especially since HANA employs it's own memory pool management you'd be looking at requests for memory that will be used for container structures of the fuzzy search...

    Probably the M_HEAP_MEMORY view is better suited for general observations.

    cheers, Lars

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  • Posted on Dec 17, 2012 at 01:24 PM

    Hello Michael,

    As Lars already said, the memory allocation shown in M_HEAP_MEMORY is dynamic.

    When you enable a fuzzy search index ('ALTER TABLE ... FUZZY SEARCH INDEX ON'), the columns that are changed are unloaded from memory. So there is no memory usage shown in M_HEAP_MEMORY.

    During the first SELECT statement that uses a column, the column is loaded into memory and the fuzzy search indexes are created. Afterwards, M_HEAP_MEMORY shows the memory used by all fuzzy search indexes that have been loaded by the SELECT statement.

    So you can check the memory usage of fuzzy search indexes without using the trace.

    Regards

    Jörg

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