Tuning areas that contain exceptionally large
database records can be difficult.
Before you begin
In this task, you will move large database
records to new areas to simplify the tuning tasks. Before you start,
review the applications that use the database and ensure that those
applications are not affected by moving such records to the new areas.
About this task
If your administration policies allow,
one possible approach to tuning areas that contain exceptionally large
database records is to define new areas that have enough CI size,
and to move these large records to the new areas before tuning the
areas.
Procedure
Complete the following steps to
define new areas and to move large database records to the new areas:
- Determine whether you can move large database records to
different areas. Then obtain the information about the large database
records to move.
Generate a Largest Database Records
report and browse the report. This report provides a list of database
records and the information about these records. Analyze the information
in the report to determine whether you can move those records or a
subset of those records to a new area that matches the record characteristics.
- Customize the randomizing module for the selected
database records and determine the DBD statements for the new areas.
You must ensure that the selected large
database records be randomized into the new areas, which means that
you must customize the randomizing routine for the database. In general,
the randomizing routine that is used needs to be a two-stage
randomizer. In this context, a two-stage randomizer determines
an area from the root sequence key value and then determines a RAP
number within the selected area.
To customize or tune the randomizing
routine, you need at least the root sequence key values for the selected
database records and information about the database record length
for each key. You can obtain this information from the Largest Database
Records report.
When you customize the randomizing routine,
be aware that the root segments of those large database records can
be randomized on different RAPs in new areas.
For the information
that you can obtain from the Largest Database Records report, see
Step 5 of
the topic Analyzing database record profile.
What to do next
Follow the steps in Tuning randomizer and DBD parameters for DEDB to tune the
areas.