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Task | Required Privilege Class |
---|---|
Define or update device classes | System or unrestricted storage |
For sequential access storage, TSM supports the following device
types:
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.
To use tape devices, you must define a device class by issuing a DEFINE DEVCLASS command with the DEVTYPE parameter.
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.
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:
Do not specify a mount limit value that is greater than the number of associated available drives in your installation. If the server tries to mount as many volumes as specified by the mount limit and no drives are available for the required volume, an error occurs and client sessions may be terminated. (This does not apply when the DRIVES parameter is specified.)
Specify a mount limit value that provides a sufficient number of mount points to support a simultaneous write to the primary storage pool and all associated copy storage pools.
A device class associated with a library can use any drive in the library that is compatible with the device class' device type. Because you can associate more than one device class with a library, a single drive in the library can be used by more than one device class. However, TSM does not manage how a drive is shared among multiple device classes.
When you associate multiple device classes of the same device type with a library, add up the mount limits for all these device classes. Ensure that this sum is no greater than the number of compatible drives.
TSM automatically cancels some processes to run other, higher priority processes. If the server is using all available drives in a device class to complete higher priority processes, lower priority processes must wait until a drive becomes available. For example, TSM cancels the process for a client backing up directly to tape if the drive being used is needed for a server migration or tape reclamation process. TSM cancels a tape reclamation process if the drive being used is needed for a client restore operation. For additional information, see Preemption of Client or Server Operations.
If processes are often canceled by other processes, consider whether you can make more drives available for TSM use. Otherwise, review your scheduling of operations to reduce the contention for drives.
This consideration also applies to the primary and copy storage pool simultaneous write function. You must have enough drives available to allow for a successful simultaneous write.
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.
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.
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 Idle Volumes.
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.
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.
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.
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.
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.
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:
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 |
Other parameters specify how to manage data storage operations involving the new device class:
You can update the device class information by issuing the UPDATE DEVCLASS command.
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 Media Devices for more information.
Removable media is treated as single-sided media. Therefore, double-sided cartridges are treated as two individual volumes in this device class. Define double-sided media as two separate volumes.
Other parameters specify how to manage storage operations involving the new device class:
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.
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.
When you define or update the FILE device class, you can specify the parameters described in the following sections.
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.
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.
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.
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.
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 |
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.
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.
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.
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.
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.
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.
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.
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.
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.