Checking Chunk I/O Activity (Informix)
Use
You can use the detailed database analysis in the SAP/Informix database monitor to check chunk input/output (I/O) activity.
Prerequisites
You need version 7.x or later of the Informix database management system (DBMS) to use the full functionality described in this procedure.
Procedure
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1. Choose Tools → CCMS →Control/Monitoring → Performance Menu →Database → Activity → Detail Analysis Menu → Chunk IO Activity (“IO” refers to disk input and output).
You can alter the kind of information you see in the display as follows:
○ By choosing different categories of information (see step 2). The system first displays Disk I/O Summary Statistics per Path.
○ By choosing a different starting point for the information (see step 3)
2. You can view different categories of information:
Choose |
To See |
With the Information |
Chunks per path |
Chunk Activity Statistics per Path |
Disk activity broken down by chunk and disk device (that is, path) |
Chunks per Dbspace |
Chunk Activity Statistics per Dbspace |
Disk activity broken down by chunk and dbspace |
Total per path |
Disk I/O Summary Statistics per Path |
Disk activity broken down by path (that is, a summary of what you see when you choose Chunks per path) |
Total per Dbspace |
Disk I/O Summary Statistics per Dbspace |
Disk activity broken down by dbspace (that is, a summary of what you see when you choose Chunks per Dbspace) |
3. You can view different starting points for the information (the system displays Informix Disk I/O Statistics Since DB Start at first):
Choose |
To |
Reset |
Set all figures to zero |
Since Reset |
Display disk activity since the last time Reset was chosen |
Since DB Start |
Display disk activity since your Informix DBMS was started |
When you choose Reset or Since Reset, the system alters the title of the display accordingly, for example:
Informix Disk I/O Statistics Since 11:39:08
4. Choose Sort with the cursor on a column heading to sort the data by that column. This is useful, for example, to see which disks have the most I/O.
The statistics used for these displays are stored in shared memory. These statistics can overrun, that is, there is no longer enough storage to hold all values. The result is negative figures – or, still later, misleading positive figures – appearing on the display. This might occur particularly if you are looking at figures since DB start. For more information about this difficulty, see SAP Note 40669.
Result
By monitoring disk I/O activity regularly, you can identify performance problems (for example, disk “hotspots”) early, so avoiding unplanned downtime. Therefore, you can make sure that the availability of your SAP System is maximized.