Monday, June 12, 2023

Datapump : Import run slow during DB migration from 12c to 19c

DB details: SAMDB and DB Size: 741.54

Export completed Time: 01:46:27 with parallel16

Import work:

  • The FULL Import began with the default parallels, namely 200GB of data were imported in 2 hours, but the rest of the tables took longer to load, as evidenced by the message "enq: Data pump "TM – contention" event It has taken more than 20 hours, but the data import for "“MD_OWNER"."PARTY_RELATION_UPDATES_AUDIT” and "MD_OWNER"."ATTRIBUTE_DELTA_AUDIT" has not been completed. Finally, an import failed due to a fatal error.

  • Huge row count mismatch in “MD_OWNER.PARTY_RELATION_UPDATES_AUDIT” as observed. As a result, " PARTY_RELATION_UPDATES_AUDIT " performed the re-import, which took more than 8hr but did not complete.

  • Performed the Metadata import and Data import option. But, during the data load observed “enq: TM – contention” and data loading with “INSERT /*+ APPEND” SQL. This import has taken a long time but didn’t complete it. 


Recommendations

Option 1: 

  • Logical Migration, Identify the top tables with a high number row count in the export log(which does not contain partitions) and exclude those tables from full import and import them individually.
  • Ensure that tablespaces (including undo and temp) have sufficient space.
  • Set parallel=2, to start the individual export for excluded tables.  
  • Ensure that the stream pool size remains at least 1 GB.
  • Skip the constraints during import and run them again after import. 

Option 2: Oracle Suggested  

  • RMAN - Physical migration, which we can complete a least downtime within 8-9 Hrs. 

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