This metric represents the number of disk writes per transaction during the sample period.
The value of this statistic is zero if there have not been any write or update transactions committed or rolled back during the last sample period. If the bulk of the activity to the database is read only, the corresponding "per second" metric of the same name is a better indicator of current performance.
This test checks the data blocks written disk per transaction. 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 |
Physical writes are %value%/transaction. |
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 |
DeltaWrites / Transactions where:
DeltaWrites: difference in 'select value from v$sysstat where name='physical writes'' between end and start of sample period
Transactions: number of transactions in sample period
Because this statistic shows both DBWR writes as well as direct writes by sessions, you should view the physical writes directly to determine where the write activity is really occurring. If the physical writes direct value comprises a large portion of the writes, then there are likely many sorts or writes to temporary tablespaces that are occurring.
If the majority of the writes are not direct, they are being performed by the DBWR writes process. This will typically only be a problem if log writer or redo waits are showing up in the Sessions Waiting for this Event page or the Top Waits page sorted by Time Waited.
Related Topics
About Alerts
About the Metric Detail Page
Editing Thresholds
Understanding Line Charts
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