Controlling Disk Usage

MPE/iX allows system managers to limit the amount of disk space a user may allocate. Disk space limitations can only be placed on MPE/iX accounts and groups. However, a limit placed on an account or group is also imposed on all hierarchical directories and files created at all levels beneath that account or group.

Users may create files outside their logon account if granted the proper access to do so. Disk usage is still accumulated to the parent account or group, regardless of who creates the file.

Users can use chown() in the MPE/iX shell or the :ALTFILE command to change the group ID of files they created outside their logon accounts to their logon account's group ID. This puts the file in the administrative domain of the user's account manager rather than in the domain of the account manager for the account in which the file is located. The disk space for the file accrues to the account in which it resides. Account managers may need to cooperate with each other or with the system administrator to manage disk space when files are being created across account boundaries.




	NOTE: No accounting limits exist for files that don't reside below MPE groups or for non-account directories under root.

To display disk usage information

The REPORT command does not show disk usage outside of the MPE account structure. In order to display disk usage for your entire system, include MPE accounts, groups and users and HFS directories, you need to use the DISKUSE command.

To display disk usage information for the current working directory, enter:

   :DISKUSE

You can also report the disk space used by a directory and all subtrees below it. To do so, enter the path followed by the TREE parameter. For example, to display disk usage for the PUB.SYS account (that is, all directories identified by the HFS specification PUB/SYS and all subdirectories below that), enter:

   :DISKUSE /SYS/PUB;TREE

The DISKUSE command displays usage information in a columnar format. Each column contains information about the directory or directories you are reviewing.

TREE: contains the total number of sectors used by the directory listed. This includes space used by the directory itself, all files in the directory, and all space used by subdirectories and files in the subtree below the directory.
LEVEL BELOW: shows the number of sectors allocated to all files and directories one level below the named directory. It does not include the space used by the directory itself or by the subtree.
DIRECTORY: displays the name of the directory in HFS format (for example, /MYACCT/MYGROUP).

To change file space limits

To change the file space limit for a group or account, use the FILES= parameter with ALTGROUP or ALTACCT. For example, to change the file space limit of the group PUB in the account ORDERS to 1000 sectors, enter:

   ALTGROUP PUB.ORDERS;FILES=1000

To add a file to a volume set

Use the BUILD command to create a file in a volume set. For example, to create the file FILE in the PUB group and add it to MPE_SYSTEM_VOLUME_SET, enter:

   BUILD FILE.PUB

Or, to create the file FILE in the DATABASE account and add it to the PROD volume set, enter:

   BUILD FILE.DATABASE

Determining Free Disk Space

Use the DISCFREE utility to determine the amount of permanent space, transient space, and free space on your system. To use DISCFREE, enter:

   DISCFREE

The DISCFREE utility:

displays information about the system's free disk space in histogram or allocation formats
determines disk volume fragmentation and transient and permanent disk space limits
shows total volume space capacity
shows disk allocation for single volumes or for the whole system

Transient storage is spread throughout the volume, and expands and contracts up to the limits configured. To optimize disk utilization, space required on a volume set is allocated on the volume with the highest percentage of free space.

System volumes should be configured with some of each type of storage. The default of 75 percent for permanent and 75 percent for transient is a recommended allocation, unless you have special needs.

If the system master PERMANENT parameter is set at 100 percent, DISCFREE shows this allocation. However, only 75 percent of the space can be allocated as permanent space on the system master volume to ensure that the system will boot. For more information about DISCFREE, refer to the MPE/iX Utilities Manual (32650-90081).

Clearing Disk Space

When jobs are aborted because of insufficient disk space, there are steps you can take to clear disk space. Some of your options include:

asking users to archive seldom-used files
setting lower account or group file space limits
decreasing the spool-file extent size
decreasing the number of events logged by the system

Use LISTFILE to see how large certain files are and when they were last accessed.

For example, to see how much space the file FILE1.TECH.MGR takes, enter:

   LISTFILE FILE1.TECH.MGR, 2

Use the ALTACCT and ALTGROUP commands with the FILES= parameter to decrease limits in accounts and groups, respectively.

For example, to decrease the file space in the group TECH to 10,000 sectors and the account manager to 100,000 sectors, enter:

   ALTGROUP TECH;FILES=10000

   ALTACCT MGR;FILES=100000

System event logs are stored in permanent files on the system volume set, so decreasing the number of events logged affects system disks only.

HFS Directories and High-Availability Products

HFS directories under MPE groups can be located on nonsystem volume sets. HFS directories under the root must reside on the system volume.

High-availability products, such as Mirrored Disk, Autorestart, and SPU Switchover, are restricted to nonsystem volume sets; therefore, they cannot support HFS directories under the root. These products only support HFS directories as descendants of MPE groups.

Controlling Disk Usage

Technical documentation

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