This is a database-level metric. For Oracle Real Application Clusters databases, this metric is monitored at the cluster database target level and not by member instances.
This metric signifies that a database user is blocking at least one other user from performing an action, such as updating a table. An alert is generated if the number of consecutive blocking occurrences reaches the specified value. The sessions being blocked can come from different instances.
Note: The catblock.sql script needs to be run on the managed database prior to using the User Blocks test. This script creates some additional tables, view, and public synonyms that are required by the User Blocks test.
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 |
8.1.7.4; 9.0.1.x; 9.2.0.x |
Every 5 Minutes |
Not Uploaded |
> |
11 |
Not Defined |
3 |
Session %sid% blocking %value% other sessions. |
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 |
Every Minute |
Every 15 Minutes |
After Every Sample |
> |
11 |
Not Defined |
3 |
Generated By Database Server |
SELECT blocking_sid, num_blocked FROM ( SELECT blocking_sid, SUM(num_blocked) num_blocked FROM ( SELECT l.id1, l.id2, MAX(DECODE(l.block, 1, i.instance_name||'-'||l.sid, 2, i.instance_name||'-'||l.sid, 0 )) blocking_sid, SUM(DECODE(l.request, 0, 0, 1 )) num_blocked FROM gv$lock l, gv$instance i WHERE ( l.block!= 0 OR l.request > 0 ) AND l.inst_id = i.inst_id GROUP BY l.id1, l.id2) GROUP BY blocking_sid ORDER BY num_blocked DESC) WHERE num_blocked != 0
Either have the user who is blocking other users rollback the transaction, or wait until the blocking transaction has been committed.
About Alerts
About the Metric Detail Page
Editing Thresholds
Understanding Line Charts
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