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Spotlight on DB2 6.9.3 - User Guide

Spotlight on IBM DB2 LUW (Linux, Unix, and Windows)
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Hash Loops alarm

The predefined Hash Loops alarm becomes active when a single partition of a hash join is larger than the available sort heap. This could indicate that you have a poorly performing hash join.

This alarm has been predefined with a Low severity level. The underlying metric for this alarm can be adjusted to suit your environment by using the Metric Editor.

What you can do

Try increasing the SHEAPTHRES for the instance or the SORTHEAP for the database or partition to alleviate this issue.

Related topics

Piped Sort Rejects alarm

The Piped Sort Rejects alarm becomes active when piped sort requests are rejected. A piped sort is rejected if the sort heap threshold is exceeded at the time the sort heap is allocated.

This alarm has been predefined with a Low severity level. The underlying metric for this alarm can be adjusted to suit your environment by using the Metric Editor.

What you can do

Increasing the sort heap threshold for the instance, or the sort heap space for the database can improve piped sort acceptance.

 

Related topics

 

Post Threshold Hash Joins alarm

The predefined Post threshold Hash Joins alarm becomes active when a hash join request was limited because of concurrent use of sort heap space (shared or private).

This alarm has been predefined with a Low severity level. The underlying metric for this alarm can be adjusted to suit your environment by using the Metric Editor.

What you can do

If this value is larger than 5% of total hash join overflows, increase the sort heap threshold (SHEAPTHRES configuration parameter).

 

Related topics

 

Post Threshold Sorts alarm

The Post Threshold Sorts alarm becomes active when a sort has been requested after the sort heap threshold has been reached. Sorts that start after the sort heap threshold (sheapthres configuration parameter) has been reached may not receive all the memory they need to run efficiently. By adjusting the sort heap threshold and sort heap size configuration parameters, you can improve sort operations and overall system performance.

This alarm has been predefined with a Low severity level. The underlying metric for this alarm can be adjusted to suit your environment by using the Metric Editor.

What you can do

If post-threshold sort values are high, you can try the following possible solutions:

  • Increasing SHEAPTHRES

  • Making SQL query changes that allow applications to use fewer or smaller sorts.

 

Related topics

Metric Editor

What are thresholds and severities?

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