[SOL-638] Replication border in Exasol 6.0 Created: 26.11.2018  Updated: 09.08.2020  Resolved: 09.08.2020

Status: Obsolete
Project: Solution Center
Component/s: EXASolution
Affects Version/s: EXASOL 6.0.0
Fix Version/s: None

Type: Explanation
Reporter: Captain EXASOL Assignee: Captain EXASOL
Labels: None

Issue Links:
Causing
is caused by EXASOL-1798 Smart and fast table replication Resolved
Related
relates SOL-639 Replication border in Exasol 6.1 Obsolete
is related to SOL-101 Replication border in EXASolution 5.0 Obsolete
Explanation:

Note: This solution is no longer maintained. For the latest information, please refer to our documentation:

https://community.exasol.com/t5/database-features/replication-border-in-exasol-6-0/ta-p/1728

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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