Date of Last Reference

The date of last reference is the date on which the file was last read or updated. If the file hasn't been read or updated since it was created, the date of last reference is the date of file creation.

The difference between the date of last reference and the date attribute (described above) is that the date of last reference is updated when a file is read—the date attribute is not.

CMS maintains the date of last reference only for files that reside in CMS file pools. It is stored in the file pool catalogs—not in the FSTs as basic file attributes are.

The date of last reference is based on Coordinated Universal Time (UTC) at the time of the reference. The date attribute, on the other hand, is based on the local time. This can cause discrepancies between the attributes, depending on the geographic location of your processor. This difference is important to remember when you are coding an application that uses the date of last reference. You might, for example, want to convert the local date to the UTC date.

For BFS files, this attribute has the same interpretation in CMS as for CMS record files. However, when stored in the catalogs this attribute is translated into a POSIX attribute called ATIME that consists of the total number of seconds from January 1, 1970.

You can use CSL routines (such as DMSEXIFI and DMSGETDX) to retrieve the date of last reference for a file. You can also use CSL routines (DMSFILEC, DMSOPEN, and DMSOPBLK) to inhibit the updating of the date of last reference. The date of last reference is intended for use by application programs. It is displayed by the FILELIST and LISTFILE commands through the use of the ALLDATES option.

For more information on how to use CSL routines, see the z/VM: CMS Application Development Guide.