This metric represents the average number of rows per sort during this sample period.
This test checks the average number of rows per sort during sample period. If the value is greater than or equal to the threshold values specified by the threshold arguments, and the number of occurrences exceeds the value specified in the "Number of Occurrences" parameter, then a warning or critical alert is generated.
The rest of the information in this section is only valid for this metric when it appears in either the Enterprise Manager Grid Control or the Enterprise Manager Database Control (if applicable).
The following table shows how often the metric's value is collected and compared against the default thresholds. The 'Consecutive Number of Occurrences Preceding Notification' column indicates the consecutive number of times the comparison against thresholds should hold TRUE before an alert is generated.
|
Target Version |
Evaluation and Collection Frequency |
Upload Frequency |
Operator |
Default Warning Threshold |
Default Critical Threshold |
Consecutive Number of Occurrences Preceding Notification |
Alert Text |
|
pre-10g |
Every 5 Minutes |
After Every Sample |
> |
Not Defined |
Not Defined |
2 |
Average sort size is %value% rows. |
|
Target Version |
Server Evaluation Frequency |
Collection Frequency |
Upload Frequency |
Operator |
Default Warning Threshold |
Default Critical Threshold |
Consecutive Number of Occurrences Preceding Notification |
Alert Text |
|
10.1.0.x; 10.2.0.x; 11.1.0.x; 11.2.0.x |
Every Minute |
Not Defined |
After Every Sample |
> |
Not Defined |
Not Defined |
2 |
Generated By Database Server |
(DeltaSortRows / (DeltaDiskSorts + DeltaMemorySorts)) * 100 where:
DeltaSortRows: difference in 'select value from v$sysstat where name='sorts (rows)'' between sample end and start
DeltaMemorySorts: difference in 'select value from v$sysstat where name='sorts (memory)'' between sample end and start
DeltaDiskSorts: difference in 'select value from v$sysstat where name='sorts (disk)'' between sample end and start
This statistic displays the average number of rows that are being processed per sort. The size provides information about the sort size of the database. This can help you to determine the SORT_AREA_SIZE appropriately. If the rows per sort are high, you should investigate the sessions and SQL performing the most sorts to see if those SQL statements can be tuned to reduce the size of the sort sample set.
The sessions that are performing the most sorts should be identified, such that the SQL they are executing can be further identified. The sort area sizes for the database may be sized correctly and the application SQL may be performing unwanted or excessive sorts. The sessions performing the most sorts are available through the Top Sessions page sorted by Disk Sorts.
Further drilldown into the session performing the most disk sorts with the Current SQL page displays the SQL statement responsible for the disk sorts.
The Top SQL page sorted by Sorts provides a mechanism to quickly display the SQL statements in the cache presented in sorted order by their number of sort operations. This is an alternative to viewing the sort of current sessions. It allows you to view sort activity via SQL statements and contains cumulative statistics for all executions of that statement.
If excessive sorts are taking place on disk and the queries are correct, consider increasing the SORT_AREA_SIZE initialization parameter to increase the size of the sort area. A larger sort area allows the Oracle Server to keep sorts in memory, reducing the number of I/O operations required to do an equivalent amount of work using the current sort area size.
Related Topics
About Alerts
About the Metric Detail Page
Editing Thresholds
Understanding Line Charts
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