Using the Realtime Monitor › Database I/O Driver Detail (PF15)

Database I/O Driver Detail (PF15)

 PM-Rnn.n SYSTEM71         CA, Inc.                  V71      08.348 15:52:14.22
 CMD-->                                                             Window : 02
                                                                    Refresh: 10
   02 Database I/O Driver Detail
     Task          Driver  Forced    Read   Write  Journal  Jrnldrvr   Read
     Number          Type   Write   Count   Count   Writes     Posts  Posts
     143         DBIOWRIT       0       0       0       0         0       0
     146         DBIOREAD       0       0       0       0         0       0
     292         DBIOWRIT       0       0       0       0         0       0

Screen Description

The Database I/O Driver Detail screen displays the I/O activity for the database I/O drivers. The screen includes one line for each driver activated for the DC/UCF system.

Database drivers are independent tasks that perform page reads and writes on behalf of a task:

Note: For more information about the read and write drivers, see the CA IDMS System Tasks and Operator Commands Guide.

What To Look For

• Look to see if Jnrldrvr Posts is high compared to Journal Writes. If it is, you may have too many read drivers activated.
• Look for a high value in the Forced Write field. A forced write occurs when the system must write a buffer page in order to read a database page. A high value means one of these conditions exist:
  • A large number of update jobs are running at the same time
  • A long-running update job is not issuing COMMIT statements frequently enough
  • Buffer activity is excessive
• Look at the values in the Read Count and Write Count fields. If the values are consistently zero, the drivers aren't doing any work and you should deactivate them.
• Monitor the number of tasks performed and system I/O. Although the drivers increase the number of tasks the system can perform, they do so at the cost of increased I/O. To use the read and write drivers most efficiently, activate them for long-running update jobs. If you use the read drivers, activate at least two to see performance improvements.