Technical data
Managing Storage Media
9.11 Managing Disk Space
Examples
1.
$ PURGE/LOG $DISK1:[JONES...]
The command in this example purges all files in the directory [JONES] and
all the subdirectories below [JONES] on the $DISK1: device. It logs the files
that are deleted (displaying their names on the terminal as they are deleted).
2.
$ PURGE/KEEP=3 $DISK1:[*...]
This example uses wildcard characters to perform global purges and uses the
/KEEP qualifier to retain only three versions of each file.
9.11.4 Setting Version Limits on Files
Another way to conserve disk space is to limit the number of file versions that
users can create in a directory by using the /VERSION_LIMIT qualifier with
the SET DIRECTORY or CREATE DIRECTORY command using the following
format:
SET DIRECTORY/VERSION_LIMIT=n
Example
$ CREATE/DIRECTORY $DISK1:[JONES]/OWNER_UIC=[200,1]/VERSION_LIMIT=3
In the example, files in account [JONES] cannot exceed three versions. If a user
in this directory attempts to exceed the three-version limit, the system purges the
file, leaving only the three most recent versions.
Note
Be careful about setting a version limit on the master file directory (MFD).
Because the system uses the version limit that you set on the MFD on
any directory you create beneath the MFD, users might inadvertently lose
important data.
9.11.5 Setting File Expiration Dates
Files–11 uses the expiration date of each file to track the use of the file. The
expiration dates aid the disposal of seldom-used files when you use the DCL
command BACKUP/DELETE.
File expiration is a file system feature that is available only on Files-11 Structure
Level 2 disks.
After you set an expiration date on a volume, the retention periods operate as
follows:
• When a user creates a file, the expiration date of the file is the current time
plus the maximum time set on the volume.
• Every time a user accesses a file (for either a read or write operation), the
current time is added to the minimum time. If the total is greater than the
expiration date, the new expiration date is used. (The new expiration date is
calculated from the maximum retention period.)
9–68 Managing Storage Media