TM Per table locks are acquired during the execution of a transaction when referencing a table with a DML statement so that the object is not dropped or altered during the execution of the transaction, if and only if the dml_locks parameter is non-zero.
TM Locks are held for base table/partition operations under the following conditions:
Enabling of referential constraints
Changing constraints from DIASABLE NOVALIDATE to DISABLE VALIDATE
Rebuild of an IOT
Create View or Alter View operations
Analyze table compute statistics or validate structure
Parallel DML operations
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 Minute |
After Every Sample |
> |
20 |
Not Defined |
3 |
%value%%% of service time is spent waiting on the 'enqueue: DML - contention' event. |
(DeltaEnqueueDMLTime/DeltaServiceTime)*100 where:
DeltaEnqueueDMLTime: difference of 'sum of time waited for sessions of foreground processes on the 'enqueue: DML - contention' event' between sample end and start
DeltaServiceTime: difference of 'sum of time waited for sessions of foreground processes on events not in IdleEvents + sum of 'CPU used when call started' for sessions of foreground processes' between sample end and start
See Idle Events
Examine the database locks page and determine the user who is blocking another user and why, then decide the appropriate action.
Related Topics
About Alerts
About the Metric Detail Page
Editing Thresholds
Understanding Line Charts
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