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    • Type: Explanation
    • Status: Published
    • Affects Version/s: EXASOL 6.0.0
    • Fix Version/s: None
    • Component/s: EXASolution
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    • Explanation:
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      Question

      What is a smart table replication and how can the replication border be modified?

      Answer

      General information on smart table replication

      • Replicates are used "on-the-fly" for local joins if a table is "small" regarding the threshold.
      • A replicated table accesses data directly from other nodes' database memories and keeps a local copy in its own DBRAM.
      • If a replicated table is modified, only changed data is reloaded into database memories of other nodes.
      • Modified tables and subselects cannot be used with smart table replication. Table replication border does not apply to those.
      • Using large replicated tables might cause decreased performance. Queries with expensive table scans (filter expressions) or between / cross joins may fall into this category.

      Soft replication border

      A table will be replicated if none of the thresholds below are reached. The table size threshold refers to the RAW_OBJECT_SIZE like in EXA_*_OBJECT_SIZES.
      The replication borders can be modified through extra database parameters in the web interface:

      -soft_replicationborder_in_numrows=<numrows> [default is 100000 rows]
      -soft_replicationborder_in_kb=<kb> [default is 1000000 -> 1GB]
      
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      Question What is a smart table replication and how can the replication border be modified? Answer General information on smart table replication Replicates are used "on-the-fly" for local joins if a table is "small" regarding the threshold. A replicated table accesses data directly from other nodes' database memories and keeps a local copy in its own DBRAM. If a replicated table is modified, only changed data is reloaded into database memories of other nodes. Modified tables and subselects cannot be used with smart table replication. Table replication border does not apply to those. Using large replicated tables might cause decreased performance. Queries with expensive table scans (filter expressions) or between / cross joins may fall into this category. Soft replication border A table will be replicated if none of the thresholds below are reached. The table size threshold refers to the RAW_OBJECT_SIZE like in EXA_*_OBJECT_SIZES. The replication borders can be modified through extra database parameters in the web interface: -soft_replicationborder_in_numrows=<numrows> [ default is 100000 rows] -soft_replicationborder_in_kb=<kb> [ default is 1000000 -> 1GB]
    • Category 1:
      Database Administration - Performance

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            • Assignee:
              CaptainEXA Captain EXASOL
              Reporter:
              CaptainEXA Captain EXASOL
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              • Created:
                Updated: