DFSDRFnn member of the IMS PROCLIB data set
Use the DFSDRFnn member of the IMS PROCLIB data set to specify that portions of the control region be placed in disabled reference (DREF) storage during initialization.
With this member, VTAM® terminal blocks (VTCBs) in DREF storage are never paged out to auxiliary storage; they remain in real or expanded storage. DFSDRFnn requires that the system have sufficient expanded storage available for the VTCBs. If you choose the DREF option for VTCBs during installation, but do not have expanded storage, the VTCBs DREF storage are page fixed.
Environments
This member of the IMS PROCLIB data set is not applicable in the DBCTL environment.
Syntax
Usage
If the VTCBs have been paged out of real storage when a checkpoint occurs, DFSDRFnn can improve the time to bring them back into real storage.
The nn suffix of DFSDRFnn is taken from the IMS procedure FIX=nn initialization parameter, the same one used for the page fixing member, DFSFIXnn (see DFSFIXnn member of the IMS PROCLIB data set).
If you specify either DFSDRFnn or DFSFIXnn, define the one you do not choose to use as a null member. For example, if you specify FIX=55, define both members (DFSDRF55 and DFSFIX55), and make the member you do not need a null member containing a blank control statement. Without both defined, IMS issues error message DFS0579, indicating a member could not be found. If DFSFIXnn is defined as a null member, message DFS0757 is issued, reminding you that no fixing requests were made.
If BLOCK=VTCB is requested in DFSFIXnn and in DFSDRFnn, the page-fix request in DFSFIXnn is ignored.
Parameters
The control information is contained in 80-character records. Continuation or sequencing must not be entered. The format is as follows:
- VTCB
- Specifies that VTCBs are loaded into DREF storage, but are never to page to auxiliary storage.