Statspack report analysis for oracle

Indicates many index reads: Wait Events Information Section The following section will describe in detail most of the sections provided in a statspack report. This level includes capturing high resource usage SQL Statements, along with all data captured by lower levels. This is best illustrated with a simplified example of few seconds in the life of an Oracle shadow process: This is the ratio of the total number of latch misses to the number of latch gets for all latches.

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Max Qry Len s. You can decrease this time by having the client bring back less data.

TX4 enqueue waits are usually the result of one of three issues. In this example, we can see 0 errors occurred during this period. When latch miss ratios are greater than 0. We want that to be large enough to be meaningful, but small enough to be relevant 15 to 30 minutes is OK.

Oracle Statspack Survival Guide

However if the actual statistic counts are small, this would not be an area of interest. This gives current memory allocation for Buffer Cache. That generally happens during many full scan of a table or Fast Full Index Scans. The times between the snapshots the collection points should, in general, be measured in minutes, not hours and never days.

These numbers are useful to diagnose CPU saturation on the system usually a query tuning issue. This gives an overall view of the load on the server. This utility will be discussed in greater detail.

Oracle Statspack Survival Guide

To prevent buffer busy waits related to data blocks, you can also use a smaller block size: Number of bytes "wasted" because redo blocks needed to be written before they are completely full.

In this example this parameter can be set to The formula to calculate the CPU usage breakdown is: The per-second statistics show you the changes in throughput i. Click stars to rate this APP! The log file sync process must wait for this to successfully complete.

When they occur in conjunction with the appearance of the 'db file scattered read' and 'db file sequential read' in the Top 5 Wait Events section, first you should examine the SQL Ordered by Physical Reads section of the report, to see if it might be helpful to tune the statements with the highest resource usage. CPU time When you are trying to eliminate bottlenecks on your system, your Statspack report's Top 5 Timed Events section is the first place to look.

If we use longer times, we begin to lose the needle in the xtatspack. SQL ordered by Buffer Gets. If your alert log shows that you are switching logs frequently that is, more than once every 15 minutesyou may be able to reduce the amount of switching by increasing the size of the online redo logs.

This is also the default snapshot level when Statspack is installed. This section is particularly useful for determining latch contention on an instance. This information may indicate which events are of interest, however it may be misleading. To address this problem, increase the size of the log files, or increase the size of the log buffer, or get faster disks to write to.

A baseline of the database's buffer pool statistics should be available to compare with the current statspack buffer pool statistics. Use LMTs, or try to preallocate extents or at least make the next extent larger for problematic dictionary-managed tablespaces. Then, using that knowledge, determine if the ratio is okay given the conditions. Note that Oracle considers average read times of greater than 20 ms unacceptable. Buffer busy waits happen when more than one transaction tries to access same block at the same time.

Maybe the application doesn't need to bring back as statspacl data as it is.

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