PMDF System Manager's Guide

Both PMDF and VMS MAIL use a number of temporary files to construct messages. These files are normally created in the SYS$SCRATCH directory. This applies to all VMS MAIL variants including PMDF MAIL, VMS MAIL, and DECwindows MAIL, but is especially important when using callable MAIL. Callable MAIL will fail under some circumstances if SYS$SCRATCH is not defined. (Specifically, callable MAIL will fail if the message is written one record at a time; this operation requires an intermediate file for storage.)

VMS MAIL creates named temporary files in whatever directory SYS$SCRATCH points to. These files generally have a .tmp extension and the word mail somewhere in the name. PMDF creates unnamed temporary files on the device SYS$SCRATCH that are not entered into any directory. Note that in either case the files are owned by the user creating them and the user must have the necessary quotas to create the file or files. No special PMDF or VMS MAIL privileges are employed to access files in SYS$SCRATCH.

PMDF can be directed to use an alternate scratch area by defining the PMDF_SCRATCH logical name. If PMDF_SCRATCH is defined PMDF will create its unnamed temporary files there. This applies to all of PMDF, not just the parts that run under VMS MAIL. If PMDF_SCRATCH is undefined or unusable PMDF will then try SYS$SCRATCH, and if SYS$SCRATCH is undefined or unusable the device associated with the current default directory will be used. If this device does not exist or is unusable PMDF will try to use SYS$LOGIN.

VMS MAIL does not use PMDF_SCRATCH for its temporary files under any circumstances, of course.