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3230934 - High CPU usage of FDA write query on SAP HANA 2.0 SPS06

Symptom

  • After upgrading to SAP HANA 2.0 SPS06 some queries are using high CPU.
  • Kernel profiler trace shows that most of the CPU is used in call "void AttributeEngine::fnBwProcessDocidsForGet2".
    E.g:

  • Thread samples show that the most dominant query uses FDA WRITE, e.g.:
    SELECT /* FDA WRITE */ DISTINCT  "BKPF" . "MANDT"...
  • Script "HANA_Threads_Callstacks_History" filtered to the timeframe of the issue and affected query shows that most threads are in call "void AttributeEngine::fnBwProcessDocidsForGet2"
    E.g.:
    ---------------------------------------------------------------------------------------------------------
    |STATEMENT_HASH  |COUNT|CALL_1                                                                          |
    ---------------------------------------------------------------------------------------------------------
    |<statement_hash>|  843|void AttributeEngine::fnBwProcessDocidsForGet2<AttributeEngine::PrefixMemoryDocu|
    |<statement_hash>|  448|void AttributeEngine::fnBwProcessDocidsForGet2<AttributeEngine::RleMemoryDocumen|
    |<statement_hash>|   65|void AttributeEngine::fnBwProcessDocidsForGet2<AttributeEngine::PrefixMemoryDocu|
    |<statement_hash>|   65|void AttributeEngine::fnBwProcessDocidsForGet2<AttributeEngine::IndirectMemoryDo|
    |<statement_hash>|   57|syscall                                                                         |
    ---------------------------------------------------------------------------------------------------------
  • Example of full call stack:
    void AttributeEngine::fnBwProcessDocidsForGet2
    int AttributeEngine::fnBwGetAggregateValueIds
    AttributeEngine::SinglePagedSpBase
    OlapEngine::Parallel::OlapAttributeApi::bwGetAggregateValueIds
    OlapEngine::Parallel::DimensionReader
    OlapEngine::Parallel::WorkerJob::run
    TRexUtils::Parallel::JobBase::runEx
    TRexUtils::Parallel::JobBase::run
    Execution::JobObjectImpl::run
    Execution::JobWorker::runJob
    Execution::JobWorker::run
    Execution::Thread::staticMainImp
    Execution::pthreadFunctionWrapper
    <no symbol>


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Environment

SAP S/4HANA with SAP HANA 2.0 SPS06

Product

SAP HANA 1.0, platform edition ; SAP HANA, platform edition 2.0

Keywords

"for all entries", NO_GROUPING_SIMPLIFICATION, CS_ITAB_IN_SUBQUERY, prefer_cs_itab_in_subquery_for_param_itab , KBA , HAN-DB-PERF , SAP HANA Database Performance , BC-DB-DBI , DB Independent Database Interface , Problem

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