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Former Member

Heap Memory Utilization is very high after SPS09 Upgrade

Experts

We recently upgraded our HANA Database from Rev 82 -92 and since then experiencing memory issues. I check the standard report "Shows Memory consumption of components" and see that system component takes 230 GB of memory ( total we have 370 GB Allocated ).

Further investigating from the view "M_SERVICE_MEMORY", found that for Indexserver, HEAP_MEMORY_ALLOCATED _SIZE=360 GB and used 350GB.

When I checked the view "M_HEAP_MEMORY", found that Page Cache "Pool/PersistenceManager/PersistentSpace(0)" was 210 GB in use. SAP Note says

"The page cache stores blocks retrieved from disk similar to a file system cache. This can e.g. speed up the access to hybrid LOBs (SAP Note 1994962). Space is reclaimed automatically by SAP HANA whenever memory is required, so a large size is not critical."

I have bounced Hana Database to see if it recliams free space, but of no use.

Few Questions:

1. Did anyone had the same issue after upgrading to SPS09.

2. How do I reduce the Heap Size ( Any parameters)

3. Am i looking at the right place to analyze the performance issue correctly.

Mahesh Shetty

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1 Answer

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    Former Member
    Mar 07, 2015 at 08:30 AM

    This is a known issue. I have now just updated SAP Note 1999997 with the following information:

    "Due to a problem with Revisions 90 to 92 the page cache size can be
    significantly increased. The allocator stack trace contains
    DataAccess::GarbageCollectorJob::run as main consumer. Upgrade to Revision 93 or
    higher in order to eliminate this issue."

    If you want you can run the allocator stack trace as described in question "How can I identify how a particular heap allocator is populated?" of SAP Note 1999997:

    mm ru

    mm flag Pool/PersistenceManager/PersistentSpace(0)/DefaultLPA/Page as

    -- Now wait until a representative amount of allocations is captured

    mm top -l 2 Pool/PersistenceManager/PersistentSpace(0)/DefaultLPA/Page

    mm ru

    mm flag Pool/PersistenceManager/PersistentSpace(0)/DefaultLPA/Page as -d

    Would be interesting to see if you also see the GarbageCollectorJob being responsible for the majority of the content.

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