Return
-
Title
Disable LOB Mapping -
Description
Capture is slow and capture trace output says that the time breakdown is being spend in Maintain the LOBMAP in Oracle most of it.
The parameter SP_OCT_UTILIZATION_TIMERS is set to 1 on source sp_ctrl:
sp_ctrl>set param SP_OCT_UTILIZATION_TIMERS 1
The Capture is allowed to run for 10 minutes with this setting of the parameter. The parameter is then reset back to the default of 0 with:
sp_ctrl>reset param SP_OCT_UTILIZATION_TIMERS
The resulting *csv* file generated in /vardir/log subdirectory is examined for troubleshooting and it shows time spent in LOBMAP maintenance is quite high relative to other stats as one of the entries in it indicate:
Date Time TotalMsec Idle GetData Checkpoint QueChkpt QueWrite Caches LobMap MiscOra Parse Ignore Process Format Latency #Chkpts #DataOps BytesRead BytesProc 11/24/2018 09:58.2 901028 0 102 650 39 56 0 375605 0 2259 77 521851 94 62735 343 938893 8679246 1165056 -
Cause
If you have PK/UK logging enabled on the source database (recommended to support more SharePlex features and faster processing), check the setting of the SP_OCT_ENABLE_LOBMAP parameter. This parameter controls whether or not SharePlex uses a LOB map when replicating tables that contain out-of-row LOB columns. The LOB map is used by the Capture process to map LOBIDs and rows when PK/UK logging is not enabled. LOB mapping is enabled by default. The SHAREPLEX_LOBMAP table stores these mappings.Transactions with numerous LOB operations can slow down Capture because it needs to maintain and refer to the mappings. If PK/UK logging is enabled on the database, you can disable LOB mapping by setting this parameter to 0. -
Resolution
Disable LOB Mapping*VERIFY THAT SUPPLEMENTAL LOGGING PK/UK IS ENABLE ON THE SOURCE DATABASE.To disable LOB mapping during active replicationRun sp_ctrl on the source system.Set SP_OCT_ENABLE_LOBMAP to 0.sp_ctrl> set param SP_OCT_ENABLE_LOBMAP 0Stop Capture.sp_ctrl> stop captureTruncate the SHAREPLEX_LOBMAP table.Restart Capture.sp_ctrl> start capture