bdfd1m1kDatabase Administration

Reducing the Number of Overflow Blocks

The following scenario addresses reducing the number of overflow blocks.

Problem

A fixed file has been defined as containing 1055-byte prime blocks. This has resulted in a large number of chained overflow blocks. Reduce this by changing the prime block size to 4095.

Solution

Reorganize the file by copying the 1055-byte prime blocks into 4095-byte prime blocks. (The application must not modify the file during the reorganization process.) You can then change the prime block size by resetting the set symbol &SW00WRS in the file DSECT. If necessary, you can also change the overflow block size by resetting &SW00ARS.

When you have done this, update the DSECT with the new &SW00WRS value, and check that the DBDEF table is ready to be loaded. Load the new DBDEF before any application accesses the data.

DSECT Set Symbols

      &SW00WRS    SETC   'L4'
      &SW00ARS    SETC   'L2'
Note:
If you omit the &SW00ARS setting, the TPFDF product uses the prime block size (&SW00WRS) value for the overflow block size.

DBDEF Statements

      DBDEF   FILE=zzzzzz,(WRS=L4,ARS=L2)




Note:
The DBDEF statement overrides any DSECT values.

Application Coding

Not applicable.