This metric represents the number of disk writes per second during the sample period. This statistic represents the rate of database blocks written from the SGA buffer cached to disk by the DBWR background process, and from the PGA by processes performing direct writes.
This test checks the data blocks written disk per second. 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%/sec. |
|
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 / Seconds where:
DeltaWrites: difference in 'select value from v$sysstat where name='physical writes'' between end and start of sample period
Seconds: number of seconds 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 actually occurring. If the physical writes direct value comprises a large portion of the writes, then there are probably many sorts or writes to temporary tablespaces occurring.
If the majority of the writes are not direct, they are being performed by the DBWR writes process. This is 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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