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Procedure documentation Checking Chunk I/O Activity (Informix)  Locate the document in its SAP Library structure

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

  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:
  1. You can view different categories of information:
    2.

    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)

  2. You can view different starting points for the information (the system displays Informix Disk I/O Statistics Since DB Start at first):
    3.

    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

  3. 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.

Note

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.

 

See also:

Listing Devices with SAPDBA

Recognition of Space Problems and Errors

Adding a Chunk with SAPDBA