The COFDLFxx parmlib member provides the name of the DLF installation exit and sets limits on the amount of storage that the system can use for Hiperbatch. To activate DLF, the CLASS statement describing the group of shared objects must be present in the active COFDLFxx parmlib member (the member named on the START command for DLF). Only one COFDLFxx member can be active at a time. . On the CLASS statement, you must supply the maximum amount of storage that your installation can use for DLF objects (MAXEXPB).
Although only one COFDLFxx member can be active at a time, you can create several members with different limit values for the storage definition parameters, MAXEXPB and PCTRETB, then use the MODIFY system command to change the active parmlib member.
You can monitor the effectiveness of the values you specify for MAXEXPB and PCTRETB through the MODIFY DLF command with the STATUS operand. If the resulting display shows that the percentage of storage in use is consistently low, you might want to switch to a COFDLFxx parmlib member that has lower limits set for MAXEXPB and PCTRETB.
IBM® supplies a default DLF parmlib member (COFDLF00) that contains a default CLASS statement. You will probably want to tailor this CLASS statement to meet your installation's needs.
You cannot replace a DLF installation exit while DLF is active. The exit requested that when DLF is started remains in effect for the duration of the DLF address space. To replace the exit, you must stop DLF, replace the exit (or change the parmlib CONEXIT parameter to specify a different exit), and then start DLF again.