The IQ server periodically evaluates the adjustable set of merge thresholds for each
RLV-enabled table, and automatically performs background (non-blocking) merges as needed. The
threshold settings can be changed, however care should be exercised before doing so because of
possible impacts on performance.
Prerequisites
- SAP Sybase IQ server has a simplex database.
- RLV storage is configured.
Task
When a merge occurs, there may be a performance impact in the server because of the
resources used by the merge.
- (Optional) Change the interval between IQ server merge evaluations.
The merge evaluator examines the merge parameters of each row-level versioning
(RLV) enabled table against configured threshold values to determine whether a
non-blocking (background) merge of the RLV table to IQ main stores should occur. You
can change the interval between activation times of the merge evaluator. If the merge
evaluator is already active or if a merge is already running when the interval ends,
the merge evaluator waits for the next interval to re-initiate.
| Database Option |
Description |
Default |
|---|
| RV_AUTO_MERGE_EVAL_INTERVAL |
Length of time between merge evaluations |
15 minutes |
- (Optional) Change the table thresholds.
When a table threshold is exceeded, a merge will be triggered for that specific
table.
| Table Threshold |
Description |
Default |
|---|
| RV_MERGE_TABLE_NUMROWS |
Number of committed RLV rows |
10 million |
| RV_MERGE_TABLE_MEMPERCENT |
Percentage of total RLV memory size |
100/ number of RLV tables |
- (Optional) Change the node threshold.
When a node threshold is exceeded, the merge condition evaluator will determine
which table(s) to merge. If multiple tables must be merged to satisfy the node
threshold, parallel merges will be triggered for each table to be merged.
| Node Threshold |
Description |
Default |
|---|
| RV_MERGE_NODE_MEMSIZE |
Total RLV memory size |
75% of configured size |