DB2 Performance Expert for Multiplatforms V2.2, 2nd Edition

302 DB2 Performance Expert for Multiplatforms V2.2

 Performance Warehouse - Expert

The Performance Warehouse is a large component of Performance Expert. It

is split into three areas:

– Processes: Which can be scheduled.

– Rules of Thumb: Which can be tailored or new ones added.

– Warehouse queries: 25 predefined queries and option to create your own.

The areas of Performance Warehouse that specifically relate to buffer pools is

covered in 5.2.4, “Performance Warehouse for buffer pool analysis” on

page 312.

 Buffer Pool Analysis

This is the menu item dedicated to investigating buffer pools. This function is

split into two main areas, which are generated simultaneously each time a

buffer pool report is created: Text Reports and Interactive Reports. The report

generation and content of these reports are described in 5.2.1, “Generating

Buffer Pool Analysis reports” on page 302.

5.2.1 Generating Buffer Pool Analysis reports

In DB2 Performance Expert, all buffer pool information is derived from DB2

snapshots. The snapshots are taken periodically as set in the Recording interval

field, in the Performance Expert Server Properties panel under the History tab. In

these examples, the snapshots are taken every 60 seconds. The information

used to populate the Buffer Pool Analysis reports is stored in the Performance

Warehouse. This data is summarized based on the Granularity for summarizing

the history data field in the Performance Expert Server Properties panel under

the Performance Warehouse tab in the client (see Figure 5-37 on page 303).

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Figure 5-37 Performance Expert Server Properties - PWH

For example, if the granularity is set to one, the history snapshots that are taken

every 60 seconds will be summarized over 15-minute periods, resulting in four

rows per hour in the Performance Warehouse tables. It is this summarization

data that is used to populate the buffer pool reports.

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The first time you access the Buffer Pool Analysis screen, no databases or

reports are displayed, as shown in Figure 5-38.

Figure 5-38 New BPA screen

The next step is to generate reports for the databases and time periods in which

you are interested. On the Buffer Pool Analysis menu bar, select File →

Generate New Report or use the toolbar button ( ).

The Report Generation dialog box is displayed (see Figure 5-39 on page 305).

From here you select the database on which you are reporting from the drop

down list, and enter the start and end times for the reporting period.

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Figure 5-39 Report Generation parameter dialog box

The End time defaults to the last time stamp of available data in PWH, and the

Start time defaults to the End time less the previously monitored period. But be

aware that the period you specify to report on may not exactly match the period

for which snapshots were taken.

In the example shown, we are reporting on a non-partitioned database, namely

PEDEMO. The Snapshot Types field determines whether we include tables in the

report, or just buffer pools and tablespaces.

Click OK to continue to the next pop-up screen, which displays the progress

generating the Text Reports and Interactive Reports (seen in Figure 5-40 on

page 306).

Note: Although the Report Generation pop-up allows you to specify very

specific start and end times, the reports will only include information from the

summarized history data in the Performance Warehouse, at best, every 15

minutes.

Therefore, it is prudent to only generate reports that are coincident with the

summarization of your warehouse reporting.

Note: The dates in the dialog box are displayed in the format of the machine

where the PE Client is installed.

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Figure 5-40 Buffer Pool Analysis Report Generation

After you have generated several reports, the Buffer Pool Analysis screen will

look similar to Figure 5-41 on page 307. The reports are grouped into Text

Reports or Interactive Reports, and further grouped by database.