Date of Last Reference

The date of last reference attribute specifies the date on which the file was last read or updated. If the file has not been read or updated since it was created, the date of last reference is the date of file creation. CMS maintains the date of last reference only for files that reside in file pools.

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

The date in the date of last reference attribute is based on Coordinated Universal Time (UTC) at the time of the reference. The date in 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 GMT 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 to retrieve the date of last reference for a file. You can also use CSL routines to inhibit the updating of the date of last reference. The date of last reference is intended for use by application programs. It is also displayed by the FILELIST and LISTFILE commands through the use of the ALLDATES option. See Using the Date of Last Reference Attribute for more information.