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Administrator's Guide


Defining and Updating Device Classes for Sequential Media


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

For sequential access storage, TSM supports the following device types:

Device Type Media Type Device Examples
3570 IBM 3570 cartridges IBM 3570 drives
3590 IBM 3590 cartridges IBM 3590, 3590E drives
4MM 4mm cartridges IBM 7206-005
8MM 8mm cartridges IBM 7208-001 and 7208-011
CARTRIDGE Tape cartridges IBM 3480, 3490, and 3490E drives
DLT Digital linear tape (DLT) cartridges DLT2000, DLT4000, DLT7000 and DLT8000 drives
DTF Digital tape format (DTF) cartridges Sony GY-2120, Sony DMS-8400 drives
ECARTRIDGE Tape cartridges StorageTek SD-3 and 9490 drives
FILE File system or storage volumes Server
GENERICTAPE Tape cartridges Tape drives supported by operating system device drivers
LTO LTO Ultrium cartridges IBM 3580, 3581, 3583, 3584
NAS Unknown Tape drives supported by the NAS file server for backups
OPTICAL 5.25-inch rewritable optical cartridges 5.25-inch optical drives
QIC Quarter-inch tape cartridges IBM 7207
REMOVABLEFILE Iomega Zip or Jaz drives, or CDROM media Removable media devices that are attached as local, removable file systems
SERVER Storage volumes or files archived in another TSM server TSM target server
WORM 5.25-inch write-once read-many (WORM) optical cartridges 5.25-inch optical drives
WORM12 12-inch write-once ready-many optical cartridges 12-inch optical drives
WORM14 14-inch write-once ready-many optical cartridges 14-inch optical drives

You can define multiple device classes for each device type. For example, you may need to specify different attributes for different storage pools that use the same type of tape drive. Variations may be required that are not specific to the device, but rather to how you want to use the device (for example, mount retention or mount limit).

For all device types other than FILE or SERVER, you must define libraries and drives to TSM before you define the device classes.

If you include the DEVCONFIG option in the dsmserv.opt file, the files you specify with that option are automatically updated with the results of this command. When you use this option, the files specified are automatically updated whenever a device class, library, or drive is defined, updated, or deleted.

The following sections explain the device classes for each supported device type.

Defining and Updating Device Classes for Tape Devices

To use tape devices, you must define a device class by issuing a DEFINE DEVCLASS command with the DEVTYPE parameter.

Note:
For upgrades from TSM Enhanced Version 2 to Version 3 or later, you must define a device class with the DEVTYPE parameter set to DLT or ECART.

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

You can update the device class by issuing the UPDATE DEVCLASS command.

Mount Limit

The MOUNTLIMIT parameter specifies the maximum number of volumes that can be simultaneously mounted for a device class. You can limit the number of drives that the device class has access to at one time with the MOUNTLIMIT parameter.

The default mount limit value is DRIVES. The DRIVES parameter indicates that every time a mount point is allocated, the number of drives online and defined to the library is used to calculate the true mount limit value. The maximum value for this parameter is 256 and the minimum value is 0. A zero value prevents new transactions from gaining access to the storage pool.

When selecting a mount limit for a device class, be sure to consider the following questions:

Note:
If the library associated with this device class is EXTERNAL type, it is recommended that you explicitly specify the mount limit instead of using MOUNTLIMIT=DRIVES.

Mount Wait Period

The MOUNTWAIT parameter specifies the maximum amount of time, in minutes, that the server waits for a drive to become available for the current mount request. The default mount wait period is 60 minutes. The maximum value for this parameter is 9999 minutes.

Note:
This parameter is not valid for EXTERNAL library types.

Mount Retention Period

The MOUNTRETENTION parameter specifies the amount of time that a mounted volume should remain mounted after its last I/O activity. If this idle time limit is reached, the server dismounts the volume. The default mount retention period is 60 minutes. The maximum value for this parameter is 9999 minutes.

Note:
A device class with DEVType=NAS allows only a value of zero (0).

For example, if the mount retention value is 60, and a mounted volume remains idle for 60 minutes, then the server dismounts the volume.

If a volume is used frequently, you can improve performance by setting a longer mount retention period to avoid unnecessary mount and dismount operations.

If mount operations are being handled by manual, operator-assisted activities, you may want to use a large mount retention period. For example, if only one operator supports your entire operation on a weekend, then define a long mount retention period so that the operator is not being asked to mount volumes every few minutes.

While TSM has a volume mounted, the drive is allocated to TSM and cannot be used for anything else. If you need to free the drive for other uses, you can cancel TSM operations that are using the drive and then dismount the volume. For example, you can cancel server migration or backup operations. For information on how to cancel processes and dismount volumes, see Canceling Server Processes and Dismounting an Idle Volume.

Tape Label Prefix

By using the PREFIX parameter, you can specify a prefix value that is used to construct the file name string that is stored in the label area of each tape volume.

The prefix string is used as the prefix of the file name that is written to the label of each tape. The default value for the tape label prefix string is ADSM.

Note:
This parameter is used primarily in the OS/390 and z/OS operating systems.

Recording Format

You can use the FORMAT parameter to specify the recording format used by TSM when writing data to removable media. See the Administrator's Reference for information about the recording formats for each device type.

Specify FORMAT=DRIVE parameter only if all drives associated with that device class are identical. If some drives associated with the device class support a higher density format than others and you specify FORMAT=DRIVE, mount errors can occur. For example, suppose a device class uses two incompatible devices such as an IBM 7208-2 and an IBM 7208-12. The server might select the high-density recording format of 8500 for each of two new volumes. Later, if the two volumes are to be mounted concurrently, one fails because only one of the drives is capable of the high-density recording format.

The recording format that TSM uses for a given volume is selected when the first piece of data is written to the volume. Updating the FORMAT parameter does not affect media that already contain data until those media are rewritten from the beginning. This process may happen after a volume is reclaimed or deleted, or after all of the data on the volume expires.

Estimated Capacity

The ESTCAPACITY parameter specifies the estimated capacity for volumes assigned to this device class. TSM estimates the capacity of the volumes in a storage pool based on the parameters assigned to the device class associated with the storage pool. For tape device classes, the default values selected by the server depend on the recording format used to write data to the volume. You can either accept the default for a given device type or specify a value.

Note:
For a device class with DEVTYPE=NAS, this value is required.

See Administrator's Reference for information about the estimated capacities of recording formats for each device type.

TSM also uses estimated capacity to determine when to begin reclamation storage pool volumes. For more information on how TSM uses the estimated capacity value, see How TSM Fills Volumes.

Library

Before the server can mount a volume, it must know which drives can be used to satisfy the mount request. This process is done by specifying the library when the device class is defined. The library must contain drives that can be used to mount the volume.

Only one library can be associated with a given device class. However, multiple device classes can reference the same library. Unless you are using the DRIVES value for MOUNTLIMIT, you must ensure that the numeric value of the mount limits of all device classes do not exceed the number of drives defined in the referenced library.

There is no default value for this parameter. It is required, and so must be specified when the device class is defined.

Defining and Updating Device Classes for Generic Tape Devices

To use a tape device that is supported by an operating system device driver, you must define a device class whose device type is GENERICTAPE.

For a manual library with multiple drives of device type GENERICTAPE, ensure that the device types and recording formats of the drives are compatible. Because the devices are controlled by the operating system device driver, the TSM server is not aware of the following:

You can update the device class information by issuing the UPDATE DEVCLASS command. Other parameters, in addition to device type, specify how to manage server storage operations:

Mount Limit
See Mount Limit.

Mount Wait Period
See Mount Wait Period.

Mount Retention Period
See Mount Retention Period.

Estimated Capacity
You can specify an estimated capacity value of any volumes defined to a storage pool categorized by a GENERICTAPE device class. The default ESTCAPACITY value for a volume in a GENERICTAPE device class is 1GB. Specify a capacity appropriate for your particular tape drive.

Library
See Library.

Defining and Updating Device Classes for Optical Devices

To use optical media, you must define a device class by issuing the DEFINE DEVCLASS command with a DEVTYPE parameter for one of the optical devices:

Parameter Description
OPTICAL 5.25-inch rewritable optical media
WORM 5.25-inch write-once optical media
WORM12 12-inch write-once optical media.
WORM14 14-inch write once optical media.

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

Mount Limit
See Mount Limit.

Mount Wait Period
See Mount Wait Period.

Mount Retention
See Mount Retention Period.

Recording Format
See Recording Format.

Estimated Capacity
See Estimated Capacity.

Library
See Library.

You can update the device class information by issuing the UPDATE DEVCLASS command.

Defining and Updating Device Classes for Removable File System Devices

Removable file devices include devices such as Iomega Zip drives or Jaz drives and CD-ROM drives. Define a device class for these devices by issuing the DEFINE DEVCLASS command with the DEVTYPE=REMOVABLEFILE parameter. See Configuring Removable File Devices for more information.

Other parameters specify how to manage storage operations involving the new device class:

Mount Wait
See Mount Wait Period.

Mount Retention
See Mount Retention Period.

Library
See Library.

Maximum Capacity

You can specify a maximum capacity value that restricts the size of volumes (that is, files) associated with a REMOVABLEFILE device class. Use the MAXCAPACITY parameter with the DEFINE DEVCLASS command.

Because the server opens only one file per physical removable medium, specify a value such that the one file makes full use of your media capacity. When the server detects that a volume has reached a size equal to the maximum capacity, it treats the volume as full and stores any new data on a different volume.

The default MAXCAPACITY value for a REMOVABLEFILE device class is the remaining space in the file system where the removable media volume is added to TSM.

You can update the device class information by issuing the UPDATE DEVCLASS command.

Defining and Updating FILE Device Classes

The FILE device type is used for storing data on disk in simulated storage volumes. The storage volumes are actually files. Data is written sequentially into standard files in the file system of the server machine. You can define this device class by issuing a DEFINE DEVCLASS command with the DEVTYPE=FILE parameter. Because each volume in a FILE device class is actually a file, a volume name must be a fully qualified file name.

Note:
Do not use raw partitions with a device class type of FILE.

When you define or update the FILE device class, you can specify the parameters described in the following sections.

Mount Limit

The mount limit value for FILE device classes is used to restrict the number of mount points (volumes or files) that can be concurrently opened for access by server storage and retrieval operations. Any attempts to access more volumes than indicated by the mount limit causes the requester to wait. The default value is 1. The maximum value for this parameter is 256.

Note:
The MOUNTLIMIT=DRIVES parameter is not valid for the FILE device class.

When selecting a mount limit for this device class, consider how many TSM processes you want to run at the same time.

TSM automatically cancels some processes to run other, higher priority processes. If the server is using all available mount points in a device class to complete higher priority processes, lower priority processes must wait until a mount point becomes available. For example, TSM cancels the process for a client backup if the mount point being used is needed for a server migration or reclamation process. TSM cancels a reclamation process if the mount point being used is needed for a client restore operation. For additional information, see Preemption of Client or Server Operations.

If processes are often cancelled by other processes, consider whether you can make more mount points available for TSM use. Otherwise, review your scheduling of operations to reduce the contention for resources.

Maximum Capacity Value

You can specify a maximum capacity value that restricts the size of volumes (that is, files) associated with a FILE device class. Use the MAXCAPACITY parameter of the DEFINE DEVCLASS command. When the server detects that a volume has reached a size equal to the maximum capacity, it treats the volume as full and stores any new data on a different volume.

The default MAXCAPACITY value for a FILE device class is 4MB.

Directory

You can specify the directory location of the files used in the FILE device class. The default is the current working directory of the server at the time the command is issued, unless the DSMSERV_DIR environment variable is set. For more information on setting the environment variable, refer to Quick Start.

The directory name identifies the location where the server places the files that represent storage volumes for this device class. While processing the command, the server expands the specified directory name into its fully qualified form, starting from the root directory.

Later, if the server needs to allocate a scratch volume, it creates a new file in this directory. The following lists the file name extension created by the server for scratch volumes depending on the type of data that is stored.

For scratch volumes used to store this data: The file extension is:
Client data .BFS
Export .EXP
Database backup .DBB
Database dump and unload .DMP

Defining and Updating SERVER Device Classes

The SERVER device type is used for special device classes whose storage volumes are not directly attached to this server. A volume with device type SERVER consists of one or more files archived in the server storage of another server, called a target server. You can define this device class by issuing a DEFINE DEVCLASS command with the DEVTYPE=SERVER parameter. For information about how to use a SERVER device class, see Using Virtual Volumes to Store Data on Another Server.

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

You can update the device class information by issuing the UPDATE DEVCLASS command.

Server Name

The TSM server on which you define a SERVER device class is called a source server. The source server uses the SERVER device class to store data on another TSM server, called a target server.

When defining a SERVER device class, specify the name of the target server. The target server must already be defined by using the DEFINE SERVER command. See Using Virtual Volumes to Store Data on Another Server for more information.

Mount Limit

Use the mount limit value for SERVER device classes to restrict the number of simultaneous sessions between the source server and the target server. Any attempts to access more sessions than indicated by the mount limit causes the requester to wait. The default mount limit value is 1. The maximum value for this parameter is 256.

Note:
The MOUNTLIMIT=DRIVES parameter is not valid for the SERVER device class.

When selecting a mount limit, consider your network load balancing and how many TSM processes you want to run at the same time.

TSM automatically cancels some processes to run other, higher priority processes. If the server is using all available sessions in a device class to complete higher priority processes, lower priority processes must wait until a session becomes available. For example, TSM cancels the process for a client backup if a session is needed for a server migration or reclamation process. TSM cancels a reclamation process if the session being used is needed for a client restore operation.

Also consider the resources available on the target server when setting mount limits. Do not set a high mount limit value if the target cannot move enough data or access enough data to satisfy all of the requests.

If processes are often cancelled by other processes, consider whether you can make more sessions available for TSM use. Otherwise, review your scheduling of operations to reduce the contention for network resources.

Maximum Capacity Value

You can specify a maximum capacity value that restricts the size of files that are created on the target server to store data for the source server. The default MAXCAPACITY value is 500MB. The storage pool volumes of this device type are explicitly set to full when the volume is closed and dismounted.

Mount Retention

You can specify the amount of time, in minutes, to retain an idle sequential access volume before dismounting it. The default value is 60. The maximum value you can specify for this parameter is 9999. A value of 1 to 5 minutes is recommended. This parameter can improve response time for sequential access media mounts by leaving previously mounted volumes online.

Prefix

You can specify a prefix that the source server will use as the beginning portion of the high-level archive file name on the target server.

Retry Period

You can specify a retry period for communications with the target server. When there is a communications failure, this period determines the amount of time during which the source server continues to attempt to connect to the target server.

Retry Interval

You can specify how often the source server tries to connect to the target server when there is a communications failure. During the retry period, the source server tries to connect again as often as indicated by the retry interval.


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