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3703467 - Long running delta merges observed on NSE Tables in HANA

Symptom

  • Long running delta merges are observed on a table in HANA according to the Mini Checks report (1999993) :

    -------------------------------------------------------------------------------------------------------------------------------------------------------------
    |CHID |DESCRIPTION                                     |HOST        |VALUE                                                        |EXPECTED_VALUE|C|SAP_NOTE|
    -------------------------------------------------------------------------------------------------------------------------------------------------------------
    |**** |SAP HANA MINI CHECKS                            |            |                                                             |              | | 1999993|
    |     |                                                |            |                                                             |              | |        |
    |M0005|Generated with                                  |            |SQL: "HANA_Configuration_MiniChecks"                         |              | | 1969700|
    |M0346|Long waitForLock savepoint phases (mid-term)    |            |8                                                            |0             |X| 2100009|
    |M0538|Long running delta merges (mid-term)            |            |/BIC/AZFA5AO0022 (5) (2646 s, 2026/01/05 07:51:31)           |none          |X| 2057046|
    |M0538|Long running delta merges (mid-term)            |            |/BIC/AZFA5AO0022 (5) (2652 s, 2026/01/05 07:51:24)           |none          |X| 2057046|
    |M0538|Long running delta merges (mid-term)            |            |/BIC/AZFA5AO0022 (5) (4648 s, 2026/01/03 00:05:13)           |none          |X| 2057046|
    |M0538|Long running delta merges (mid-term)            |            |/BIC/AZFA5AO0022 (5) (4653 s, 2026/01/03 00:05:06)           |none          |X| 2057046|
    |M0554|Tables with long resource wait times (mid-term) |            |/BIC/AZFA5AO0022 (2046 s, 2026/01/08 11:16:51)               |none          |X| 2057046|
    |M0554|Tables with long resource wait times (mid-term) |            |/BIC/AZFA5AO0022 (2644 s, 2026/01/05 07:51:31)               |none          |X| 2057046|
    |M0554|Tables with long resource wait times (mid-term) |            |/BIC/AZFA5AO0022 (4646 s, 2026/01/03 00:05:13)               |none          |X| 2057046|

  

 

  • M_CS_TABLES view shows that the table is an NSE page loadable object :
      
    ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
    |HOST      |   PORT|SCHEMA_NAME|TABLE_NAME      |PART_ID|MEMORY_SIZE_IN_MAIN|MEMORY_SIZE_IN_TOTAL|MEMORY_SIZE_IN_DELTA|  RECORD_COUNT|RAW_RECORD_COUNT_IN_MAIN|RAW_RECORD_COUNT_IN_DELTA|LOAD_UNIT|
    ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

    |Hostname|30.040 |SAPHANADB  |/BIC/AZFA5AO0022|     1 |     3.881.291.792 |      3.881.873.912 |            555.400 |  114.646.679 |            114.646.679 |                       0 |PAGE     |
    |Hostname|30.040 |SAPHANADB  |/BIC/AZFA5AO0022|     2 |     2.065.179.392 |      2.111.650.526 |         46.176.038 |  160.013.671 |            160.013.671 |                 104.115 |PAGE     |
    |Hostname|30.040 |SAPHANADB  |/BIC/AZFA5AO0022|     3 |     6.128.146.236 |      6.128.728.356 |            555.400 |  736.038.447 |            736.038.447 |                       0 |PAGE     |
    |Hostname|30.040 |SAPHANADB  |/BIC/AZFA5AO0022|     4 |     5.437.842.400 |      5.590.130.962 |        151.987.562 |1.008.563.833 |          1.008.563.833 |                 402.874 |PAGE     |
    |Hostname|30.040 |SAPHANADB  |/BIC/AZFA5AO0022|     5 |    37.974.644.532 |     38.477.272.422 |        498.641.138 |1.141.786.510 |          1.141.786.510 |               1.333.773 |PAGE     |
    |Hostname|30.040 |SAPHANADB  |/BIC/AZFA5AO0022|     6 |     1.278.811.844 |      1.279.393.124 |            555.400 |   32.797.395 |             32.797.395 |                       0 |PAGE     |
    |Hostname|30.040 |SAPHANADB  |/BIC/AZFA5AO0022|     7 |           272.320 |            848.360 |            559.360 |            0 |                      0 |                       0 |PAGE     |
    |Hostname|30.040 |SAPHANADB  |/BIC/AZFA5AO0022|     8 |           272.320 |            848.360 |            559.360 |            0 |                      0 |                       0 |PAGE     |
    |Hostname|30.040 |SAPHANADB  |/BIC/AZFA5AO0022|     9 |         2.070.200 |          2.649.476 |            559.500 |       80.788 |                 80.788 |                       0 |PAGE     |
    ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

 

  • NSE cache statistics give more detail 'HANA_NSE_BufferCache_Tables_2.00.040+.txt'
     
    ----------------------------------------------------------------------------------------------
    |HOST      |PORT |TOT_BUFF_GB|SCHEMA_NAME|TABLE_NAME      |PAGED_GB|BUFF_GB|BUFF_PCT|USED_PCT|
    ----------------------------------------------------------------------------------------------
    |Hostname|30040|     289.97|SAPHANADB  |/BIC/AZFA5AO0022|  297.66|  51.74|   17.38|   17.84|
    ----------------------------------------------------------------------------------------------

 

  • There may also be savepoints blocked while waiting for the delta merge processing in thread callstack state : "AttributeEngine::IndirectPagedDocuments::compress" 

    indexserver_Hostname.port.rtedump.xx-xx.xx.savepoint_blocked.trc

    [SAVEPOINT_SHAREDLOCK_OWNERS]  Owners of shared SavepointLocks: (2026-01-08 11:24:15 149 Local)
    20100966226[thr=1192372]: JobWrk833726, TID: 558, UTID: 9503241553, CID: -1, LCID: 0, SEID: 0, parent: 2878313, SQLUserName: "", AppUserName: "", AppName: "", ConnCtx: ---, StmtCtx: ---, WorkloadCtx: ---, NUMA node: 6, type: "JobWorker", method: "prepareDeltaMerge", detail: "IndexName: SAPHANADB:_SYS_SPLIT_/BIC/AZFA5AO0022~5 Attribute: 259/DEB_CRE_L3", command: "" at 0x00007f9d9098f480 in AttributeEngine::IndirectPagedDocuments::compress(TRexUtils::IndexVector const&, unsigned int)+0xc90 at ltt/ext/array_base.hpp:604 (libhdbcs.so)
    [OK] in 00:00:00 011
    --

    20100966226[thr=1192372]: JobWrk833726 at
       0: 0x00007f9d9098f480 in AttributeEngine::IndirectPagedDocuments::compress(TRexUtils::IndexVector const&, unsigned int)+0xc90 at ltt/ext/array_base.hpp:604 (libhdbcs.so)
       1: 0x00007f9d9383c282 in AttributeEngine::SpAttribute<TrexTypes::FixedAttributeValue8, AttributeEngine::ValueDict<TrexTypes::FixedAttributeValue8>, AttributeEngine::PagedDocuments>::mergeOldIntoNew(AttributeEngine::AttributeValueContainer const&, AttributeEngine::DeltaMerge::AttributeMergeData&)+0x490 at AttributeEngine/Main/Compression/PagedDocuments.h:60 (libhdbcs.so)
       2: 0x00007f9d9626cf02 in AttributeEngine::MemoryAvc2::prepareDeltaMerge(AttributeEngine::AttributeValueContainer&, AttributeEngine::DeltaMerge::AttributeMergeData&)+0xa0 at AttributeEngine/AttributeValueContainer.cpp:3142 (libhdbcs.so)
       3: 0x00007f9d9602a5bb in AttributeEngine::AttributeApi::prepareDeltaMerge(TrexBase::IndexName const&, AttributeEngine::DeltaMerge::AttributeMergeData&)+0x627 at AttributeEngine/AttributeApi.cpp:1646 (libhdbcs.so)
       4: 0x00007f9da683adec in TRexAPI::MergeAttributeJob::doMerge(TRexAPI::ColumnMergeData&, TRexAPI::DeltaMergeState&, bool)+0x48 at ims_search_api/DeltaMerge/MergeAttributeJob.cpp:176 (libhdbcsapi.so)
       5: 0x00007f9da683b8af in TRexAPI::MergeAttributeJob::run(Execution::Context&, Execution::JobObject&)+0x19b at ims_search_api/DeltaMerge/MergeAttributeJob.cpp:293 (libhdbcsapi.so)
       6: 0x00007f9d809cffcb in Execution::JobObjectImpl::run(Execution::JobWorker*)+0x13d7 at Basis/Execution/impl/JobExecutorRunJob.cpp:772 (libhdbbasis.so)
       7: 0x00007f9d809d782a in Execution::JobWorker::runJob(ltt::smartptr_handle<Execution::JobObjectForHandle>&)+0x8a6 at Basis/Execution/impl/JobExecutorThreads.cpp:379 (libhdbbasis.so)
       8: 0x00007f9d809d9518 in Execution::JobWorker::run(Execution::ThreadRC&)+0x744 at Basis/Execution/impl/JobExecutorThreads.cpp:1382 (libhdbbasis.so)
       9: 0x00007f9d80a1a9e0 in Execution::Thread::staticMainImp(Execution::Thread*)+0x610 at Basis/Execution/impl/Thread.cpp:605 (libhdbbasis.so)
      10: 0x00007f9d80a213bf in Execution::pthreadFunctionWrapper(Execution::Thread*)+0x1eb at Basis/Execution/impl/ThreadInterposition.cpp:691 (libhdbbasis.so)
      11: 0x00007f9d7ffbf1ca in start_thread+0xe6 (libpthread.so.0)
      12: 0x00007f9d7ea3ce63 in __GI___clone+0x40 (libc.so.6)
      
      
    20100966226[thr=1192372]: JobWrk833726, TID: 558, UTID: 9503241553, CID: -1, LCID: 0, SEID: 0, parent: 2878313, SQLUserName: "", AppUserName: "", AppName: "", ConnCtx: ---, StmtCtx: ---, WorkloadCtx: ---, NUMA node: 6, type: "JobWorker", method: "prepareDeltaMerge", detail: "IndexName: SAPHANADB:_SYS_SPLIT_/BIC/AZFA5AO0022~5 Attribute: 259/DEB_CRE_L3", command: "" at 0x00007f9d9098eea2 in AttributeEngine::IndirectPagedDocuments::compress(TRexUtils::IndexVector const&, unsigned int)+0x6b2 at AttributeEngine/Main/Compression/IndirectDocumentsBase.cpp:332 (libhdbcs.so)
    "JobWrk833726";20100966226;1192372;0x00007be00f640800;"Running";-1;"";"";558;9503241553;"JobWorker";"prepareDeltaMerge";"IndexName: SAPHANADB:_SYS_SPLIT_/BIC/AZFA5AO0022~5 Attribute: 259/DEB_CRE_L3";"";2878313;"(no wait)";18446744073709551615;"(no wait)";1767841903824062;19;11031042;0;28721635791;122403;0x00007f9ac4bfd000;2371584;131072;450414;74277380;376136465;0;0
    "JobWrk833726";6;6;2248671;0;"3";"prepareDeltaMerge";0;0;0;"Running";0;0


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Environment

SAP HANA Platform Edition 2.0   

Product

SAP HANA, platform edition 2.0

Keywords

NSE, Page Loadable, Delta Merge, Performance , NSE buffer size, optimization, Native Storage Extension, AttributeEngine::IndirectPagedDocuments::compress , KBA , HAN-DB-NSE , SAP HANA Native Storage Extension , HAN-DB-PERF , SAP HANA Database Performance , Problem

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