bdfd1m1qDatabase Administration

Specifying a Lower Packing Limit

The following scenario addresses specifying a lower packing limit.

Problem

A TPFDF file is heavily read and updated. Because there are frequent DBDEL macros, each subfile is packed to 100%.

This is efficient for reading LRECs, but unsatisfactory when an application is adding new LRECs to the middle of a subfile. Because the subfile is so fully packed, when the TPFDF product adds or replaces an LREC, it may have to move some of the LRECs to an overflow block. This creates an unnecessary processing overhead.

Solution

When the TPFDF product packs this subfile, it normally packs each block to 100%. You can use the PLI parameter in the DBDEF to override this by specifying that the TPFDF product should pack blocks only up to a particular limit, not to 100%. Each block then has some space available for subsequent DBADD macros or dfadd functions.

In the DBDEF, specify a PLI value between the default packing limit for the subfile and 100%. The default packing density is 50% for L2 blocks, and 75% for L4 blocks.

DSECT Set Symbols

Not applicable.

DBDEF Statements

      DBDEF   FILE=zzzzzz,PLI=80

Application Coding

Not applicable.