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  1. Solution Center
  2. SOL-101

Replication border in EXASolution 5.0

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    • Type: Explanation
    • Status: Obsolete
    • Affects Version/s: EXASolution 5.0.0
    • Fix Version/s: None
    • Component/s: EXASolution
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      General information on replication

      • Replicates are created "on-the-fly" for joins if a table is "small" regarding the thresholds
      • A replicated table resides in the main memory of each node. A replicated table needs n*MEM_SIZE main memory (n = number of active database nodes, MEM_SIZE = MEM_OBJECT_SIZE of the table)
      • Once created a replicate can be reused for further queries
      • A replicate is dropped on any DML on the table
      • Using large replicated tables might cause decreased performance, because every node does all the work and the rows that are not located on a specific node are filtered out at the end of processing.

      Soft replication border

      A table will be replicated if none of the thresholds below is reached. For cross joins of a table with itself this border is also the maximum size allowed. The table size threshold refers to the RAW_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]
      

      Hard replication border

      Hard thresholds define which tables will not be replicated (please note that the system will not start if hard border < small border). Those thresholds are important for the enforced replication for cross joins. The limit affects only enforced replication for cross joins between different tables, for identical tables the much lower soft replication border is the upper bound.

      -hard_replicationborder_in_numrows=<numrows> [default is 5000000 rows]
      -hard_replicationborder_in_kb=<kb> [default is 5000000 -> 5GB]
      
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      General information on replication Replicates are created "on-the-fly" for joins if a table is "small" regarding the thresholds A replicated table resides in the main memory of each node. A replicated table needs n*MEM_SIZE main memory (n = number of active database nodes, MEM_SIZE = MEM_OBJECT_SIZE of the table) Once created a replicate can be reused for further queries A replicate is dropped on any DML on the table Using large replicated tables might cause decreased performance, because every node does all the work and the rows that are not located on a specific node are filtered out at the end of processing. Soft replication border A table will be replicated if none of the thresholds below is reached. For cross joins of a table with itself this border is also the maximum size allowed. The table size threshold refers to the RAW_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] Hard replication border Hard thresholds define which tables will not be replicated (please note that the system will not start if hard border < small border). Those thresholds are important for the enforced replication for cross joins. The limit affects only enforced replication for cross joins between different tables, for identical tables the much lower soft replication border is the upper bound. -hard_replicationborder_in_numrows=<numrows> [ default is 5000000 rows] -hard_replicationborder_in_kb=<kb> [ default is 5000000 -> 5GB]
    • Category 1:
      Database Administration - Performance

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            • Assignee:
              CaptainEXA Captain EXASOL
              Reporter:
              CaptainEXA Captain EXASOL
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