Database Writer Average Scan Depth (DBWRAvgScanDepth)
This parameter graphs the average scan depth (number of buffers examined by DBWR) that is added to this statistic every time DBWR scans the LRU for dirty buffers.
Recommendations
If your system has to scan too many buffers in the foreground to find a free buffer, it wastes CPU resources. To alleviate this problem, tune the DBWn process(es) to write more frequently.
You can also increase the size of the buffer cache to enable the database writer process(es) to keep up. To find the average number of buffers that the system scans at the end of the least recently used list (LRU) to find a free buffer, use the following formula:
1 + value of free buffers inspected / free buffers inspected = avg. buffers scanned
Normally you would expect to see 1 or 2 buffers scanned, on average. If more than this number are being scanned, increase the size of the buffer cache or tune the DBWn process(es).
BMC PATROL properties
Attribute | Default value |
|---|---|
Application class | ORACLE_PERFORMANCE |
Command type | not applicable |
Platform | all |
Icon style | Graph |
Unit | average number of buffers |
Border range | undefined |
Alarm1 range | undefined |
Alarm2 range | undefined |
Scheduling(poll time) | poll time of collector |
Active at installation | Yes |
Parameter type | Consumer |
Value set by | CollPerformance |
BMC ProactiveNet Performance Management properties
Property | Default value |
|---|---|
| Monitor type | Oracle Database Performance |
| Key Performance Indicator | No |
| Monitor for abnormalities | No |
| Graph by default | No |
| Availability | No |
| Response time | No |
| Normal distribution | Yes |
| Statistical | Yes |
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