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Administrator's Guide


Defining and Updating Tape Device Classes


Task Required Privilege Class
Define or update device classes System or unrestricted storage

You can define and update tape device classes to support the tape devices and storage media available at your installation. When you define the device class, specify the device type of either 3590 or CARTRIDGE.

The following parameters specify how to manage data storage operations involving the new device class:

Mount Limit

Most installations have a limited number of tape drives available at any one time. When defining tape device classes, you can limit the number of simultaneous tape mounts to efficiently use your tape devices. The mount limit specifies the maximum number of volumes that can be mounted simultaneously for a device class. Your goal in setting a tape mount limit is to guarantee that a number of tape mounts will be available to respond to a user request for restoring, retrieving, or recalling a file.

If you do not set a tape mount limit, then the server sets the tape mount limit to two. The maximum number of tape mounts per device class supported by Tivoli Storage Manager is 256.

To determine a tape mount limit for each device class, consider:

Mount Wait Period

You can use the MOUNTWAIT parameter to specify the maximum amount of time, in minutes, that the server waits for a manual (or operator controlled) volume mount request to be satisfied before canceling the request. The default mount wait period is 60 minutes. The maximum value for this parameter is 9999 minutes.

Note:
When an ATL is involved, mount point preemption may result in message IEC147I being issued with completion code 613-1C, followed by message CBR4161I with a system completion code and a reason code. When no ATL is involved, an indication of an ABEND with a system completion may occur. These ABENDs and indications, which are associated with the canceling of a tape mount request, can be ignored because the server will recover from the ABEND and continue normal operations.

Mount Retention Period

In addition to setting a tape mount limit, you can specify a mount retention period for each device class. The mount retention period is the maximum amount of time, in minutes, that the server retains a mounted tape that is not being used before it dismounts the tape. The system sets a default of 60 minutes. Mount retention time does not begin until the tape is considered idle. The following sequence occurs:

  1. When the task being performed by the last client using the mounted tape has completed, that client's idletimeout clock begins.
  2. When the idletimeout expires, that client session ends.
  3. The mount retention time starts.
  4. When the mount retention time expires, the tape is dismounted.

The duration of mount retention is the IDLETIMEOUT option of the last client using the tape plus the mount retention value. The IDLETIMEOUT option is in the server options file. The mount retention period is a parameter of the define device class command. For example, if a mounted tape volume remains idle for 60 minutes, then the server dismounts the tape volume from the tape device.

When a tape volume is needed frequently, you can improve performance by setting a longer mount retention period to avoid unnecessary tape mounts.

For manually mounted tape libraries, consider how many tape devices you group in each device class in relation to the number of tape operators who monitor those tape devices. For example, if only one tape operator supports your entire tape library on a weekend, then define a long mount retention period so that the operator is not asked to mount tapes every few minutes.

Maximum Capacity

You can specify the maximum amount of data that Tivoli Storage Manager stores in a volume in the device class. If you do not specify a value for a device class with the CARTRIDGE device type, Tivoli Storage Manager uses a default method based on IBM 3480 and 3490E device characteristics by using IBM tapes. If the default method does not meet your needs, set the value to less than the maximum capacity of the tape to avoid an end-of-tape situation.

For a device class with the 3590 device type, the tapes are filled to the either the physical end of the tape or the value you specify as the maximum capacity.

If you specify a maximum capacity and Tivoli Storage Manager detects the end of the tape before reaching this capacity for a volume, a warning message is issued and the tape is treated as full.

File Expiration Date

For each tape device class, you can specify an expiration date, which is placed in the tape label. Use the date format of yyyymmdd or yyyyddmm.

Tivoli Storage Manager ensures that tape volumes with existing data on them are not overwritten. This process is useful for protecting workstation files from being overwritten by another tape management system. Set this date to match the expiration date defined by the EXPDT parameter in your current JCL.

To not set an expiration date is the system default. If you specify 99365, an operator must verify whether or not the tape volume can be overwritten. If you define an expiration date, then you cannot define a retention period as described in File Retention Period.

MVS Device Unit Name

Specify a unit name to define a group of tape devices that support 3590 or cartridge tape, as previously defined in your JCL.

The unit name can be:

For example, the esoteric unit name for a group of 3480 Magnetic Tape Subsystem devices with the Improved Data Recording Capability (IDRC) feature might be 3480XF. Or you could name a group of 3490 Magnetic Tape Subsystem devices that use Enhanced Capacity Cartridge System Tape (ECCST) as 3490LONG.

Data Compression

Identify whether the device class supports the compression of data on tape volumes. Data compression is dependent on whether or not the tape device should exploit a hardware compaction feature, such as IDRC.

As a default, the system sets the compression attribute to yes. If your tape devices have a compression feature, then files are compressed when written to cartridge tape. If your tape devices do not have a compression feature, then the compression attribute is ignored and files are not compressed when written to tape.

If you plan to transport tapes to other physical sites, ensure that the second location has the capability of reading compressed data from the tapes. If the alternate site cannot read compressed data, set compression to no.

Tape Volume Prefix

For each tape device class, define a tape volume prefix. The tape volume prefix is the high-level qualifier of the data set name in the standard tape label. Tivoli Storage Manager provides a default tape volume prefix named ADSM.

When an empty cartridge system tape is mounted, the system creates a tape label with the data set name ADSM.BFS to indicate that this tape volume is used by Tivoli Storage Manager for data storage.

If you have already established a tape label data set naming convention that supports your current tape management system, consider using a tape volume prefix that conforms to your naming convention.

Determine whether you are cataloging your current tape volumes. Because the Tivoli Storage Manager server does not catalog tape volumes, you should use the tape volume prefix to establish external security protection for cataloged tape volumes by using a security manager such as RACF.

Protection Status

For each tape device class, you can set a protection attribute to YES, NO, or AUTOMATIC, as previously defined in your JCL. The PROTECTION parameter updates the RACF profile to identify which users have access to tape volumes associated with the device class.

As a default, the system sets the protection attribute to no. When set to no, any cataloged tape volumes use the generic RACF profile. If you set the protection attribute to yes, RACF uses the entire data set name. This allows you to define specific protection criteria for tape volumes associated with the device class.

If you specify PROTECTION=AUTOMATIC, Tivoli Storage Manager issues RACROUTE commands to delete profiles when a volume is deleted from Tivoli Storage Manager. The deletion commands issued depend on the current system settings for TAPEVOL and TAPEDSN. If the system settings are changed, Tivoli Storage Manager may not delete existing profiles.

Choosing RACF Protection Status

If sensitive data is stored on volumes assigned to this device class, it is recommended that PROTECTION=YES be specified and that RACF profiles be manually deleted after tape cartridges have been erased.

The profiles created when you specify PROTECTION=YES or PROTECTION=AUTOMATIC depend on the system RACF settings. The protection provided is the same as using PROTECT=YES in JCL. If RACF is active and both TAPEVOL and TAPEDSN are inactive, allocation of tapes will fail. See RACF Security Administrator's Guide for more information on the TAPEVOL and TAPEDSN settings and the profiles that will be created when they are active.

Profile creation and deletion occur based on the protection setting when the volume is first used and when it is deleted. Tivoli Storage Manager does not attempt to create profiles for volumes that it has already used. If protection is set to AUTOMATIC, Tivoli Storage Manager will attempt to delete profiles when volumes are deleted.

Do not change protection to AUTOMATIC for a device class that has been set to NO. Volumes without profiles may exist and error messages will be generated when volumes are deleted. If a different value is required, a new device class should be defined.

File Retention Period

For cartridge tapes, you have the option of setting a retention period to specify how long files should be retained on tape. The retention period can only be used if you do not specify an expiration date.

While Tivoli Storage Manager does not use the retention period, the server does pass the information to the MVS operating system to ensure that other tape management systems do not overwrite tape volumes that contain retained data.

For example, if you specify a retention period of 365 days, then existing tape management systems do not overwrite files on these tapes until 365 days have passed.

Use this parameter to match the retention period specified by the RETPD parameter in your current JCL. If you do not specify a value for the retention period, Tivoli Storage Manager sets the default to none. The maximum number of retention days that you can specify is 9999 days.

Estimated Capacity

Tivoli Storage Manager estimates the capacity of tape volumes assigned to storage pools categorized by device class. You can use these system defaults to plan for and monitor the use of your storage media.

The estimated capacity is used by the server to generate storage pool and storage volume reports. When volumes are written and filled, the server determines the actual capacity of the tape volume and uses this instead of the estimated capacity.

You can adjust the estimated capacity to more accurately reflect the capacity of your storage media.

Tivoli Storage Manager uses a default estimated capacity of 9GB for 3590 tapes.

See Administrator's Reference for information about the estimated capacities used by Tivoli Storage Manager for cartridge system tapes.

Example: 3480 Devices

In this example, define a device class named 3480XF to represent 3480 Magnetic Tape Subsystem devices with the IDRC feature.

Based on user requirements, set the expiration date to 99365 so that the files on these tape volumes are not expired by other tape management systems unless a tape operator overrides the expiration date. Set protection to yes so that RACF, if installed, protects the volumes assigned to this device class.

Next, use the esoteric unit name 3480 to identify that this device class supports 3480 device classes with the IDRC feature, and increase the estimated capacity to 200 MB.

Finally, use the system defaults to limit the number of tape mounts to 2, set a mount retention period of 60 minutes, set compression to yes, and use ADSM as the tape volume prefix.

To define the device class named 3480XF, enter:

define devclass 3480xf devtype=cartridge
expiration=99365 protection=yes
unit=3480 estcapacity=200m


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