DEFINE DEVCLASS (Define a 4MM device class)

Use the 4MM device class when you are using 4 mm tape devices.

Privilege class

To issue this command, you must have system privilege or unrestricted storage privilege.

Syntax


>>-DEFine DEVclass--device_class_name--------------------------->

>--LIBRary--=--library_name--DEVType--=--4MM-------------------->

   .-FORMAT--=--DRIVE-----.                             
>--+----------------------+--+----------------------+----------->
   '-FORMAT--=--+-DRIVE-+-'  '-ESTCAPacity--=--size-'   
                +-DDS1--+                               
                +-DDS1C-+                               
                +-DDS2--+                               
                +-DDS2C-+                               
                +-DDS3--+                               
                +-DDS3C-+                               
                +-DDS4--+                               
                +-DDS4C-+                               
                +-DDS5--+                               
                +-DDS5C-+                               
                +-DDS6--+                               
                '-DDS6C-'                               

   .-PREFIX--=--ADSM-------------------.   
>--+-----------------------------------+------------------------>
   '-PREFIX--=--+-ADSM---------------+-'   
                '-tape_volume_prefix-'     

   .-MOUNTWait--=--60------.  .-MOUNTRetention--=--60------.   
>--+-----------------------+--+----------------------------+---->
   '-MOUNTWait--=--minutes-'  '-MOUNTRetention--=--minutes-'   

   .-MOUNTLimit--=--DRIVES-----.   
>--+---------------------------+-------------------------------><
   '-MOUNTLimit--=--+-DRIVES-+-'   
                    +-number-+     
                    '-0------'

Parameters

device_class_name (Required)

Specifies the name of the device class to be defined. The maximum length of the device class name is 30 characters.

LIBRary (Required)

Specifies the name of the defined library object that contains the 4 mm tape drives used by this device class. For information about defining a library object, see the DEFINE LIBRARY command.

DEVType=4MM (Required)

Specifies that the 4MM device type is assigned to the device class. The 4MM indicates that 4 mm tape devices are assigned to this device class.

FORMAT

Specifies the recording format to be used when data is written to sequential access media. This parameter is optional. The default value is DRIVE.

If the drives are in a library that includes drives of different tape technology, do not use the DRIVE value. Use the specific format that the drives use.

The following table lists the recording formats and estimated capacities for 4 mm devices:

Table 1. Recording formats and default estimated capacities for 4 mm tapes
Format	Estimated Capacity	Description
DRIVE	–	The server selects the highest format that is supported by the drive on which a volume is mounted. Attention: Avoid specifying DRIVE when a mixture of drives is used within the same library. For example, do not use this option for a library that contains some drives that support recording formats superior to other drives.
DDS1	2.6 GB (60 meter) 4.0 GB (90 meter)	Uncompressed format, applies only to 60-meter and 90-meter tapes
DDS1C	See note 1.3 GB (60 meter) 2.0 GB (90 meter)	Compressed format, applies only to 60-meter and 90-meter tapes
DDS2	4.0 GB	Uncompressed format, applies only to 120-meter tapes
DDS2C	See note 8.0 GB	Compressed format, applies only to 120-meter tapes
DDS3	12.0 GB	Uncompressed format, applies only to 125-meter tapes
DDS3C	See note 24.0 GB	Compressed format, applies only to 125-meter tapes
DDS4	20.0 GB	Uncompressed format, applies only to 150-meter tapes
DDS4C	See note 40.0 GB	Compressed format, applies only to 150-meter tapes
DDS5	36 GB	Uncompressed format, when using DAT 72 media
DDS5C	See note 72 GB	Compressed format, when using DAT 72 media
DDS6	80 GB	Uncompressed format, when using DAT 160 media
DDS6C	See note 160 GB	Compressed format, when using DAT 160 media
Note: If this format uses the tape drive hardware compression feature, depending on the effectiveness of compression, the actual capacity might be greater than the listed value.

ESTCAPacity

Specifies the estimated capacity for the volumes that are assigned to this device class. This parameter is optional.

You can specify this parameter if the default estimated capacity for the device class is inaccurate due to compression of data.

You must specify this value as an integer followed by one of the following unit indicators: K (kilobytes), M (megabytes), G (gigabytes), or T (terabytes). The smallest value that is accepted is 1 MB (ESTCAPACITY=1M).

For example, specify that the estimated capacity is 9 GB with the parameter ESTCAPACITY=9G.

For more information about the default estimated capacity for 4 mm tapes, see Table 1

PREFIX

Specifies the high-level qualifier of the file name that the server writes into the sequential access media labels. For each sequential access volume assigned to this device class, the server uses this prefix to create the data set name. This parameter is optional. The default is ADSM. The maximum length of this prefix is 8 characters.

If you have a naming convention for media labels to support your current management system, use a volume prefix that conforms to your naming conventions.

Values that are specified for this parameter must meet the following conditions:

The value is to be made up of qualifiers, which can be a maximum of eight characters including periods. For example, the following value is acceptable:
```
     AB.CD2.E
```
The qualifiers must be separated by a single period.
The first letter of each qualifier must be alphabetic or national (@,#,$), followed by alphabetic, national, hyphen, or numeric characters.

An example of a tape volume data set name using the default prefix is ADSM.BFS.

MOUNTRetention

Specifies the number of minutes that an idle sequential access volume is retained before it is dismounted. This parameter is optional. The default value is 60 minutes. You can specify a number 0 - 9999.

This parameter can improve response time for sequential access media mounts by leaving previously mounted volumes online.

However, for EXTERNAL library types (that is, a library that is managed by an external media management system), set this parameter to a low value (for example, two minutes) to enhance device sharing between applications.

Note: For environments in which devices are shared across storage applications, the MOUNTRETENTION setting must be carefully considered. This parameter determines how long an idle volume remains in a drive. Some media managers do not dismount an allocated drive to satisfy pending requests. You might need to tune this parameter to satisfy competing mount requests while maintaining optimal system performance. Typically, problems arise more frequently when the MOUNTRETENTION parameter is set to a value that is too small, for example, zero.

MOUNTWait

Specifies the maximum number of minutes the server waits for an operator to respond to a request to either mount a volume in a drive in a manual library or check in a volume to be mounted in an automated library. This parameter is optional. If the mount request is not satisfied within the specified amount of time, the mount request is canceled. The default value is 60 minutes. You can specify a number 0 - 9999.

MOUNTLimit

Specifies the maximum number of sequential access volumes that can be simultaneously mounted for the device class. This parameter is optional. The default is DRIVES. You can specify a number 0 - 4096.

If you plan to use the simultaneous-write function, ensure that sufficient drives are available for the write operation. If the number of drives needed for a simultaneous-write operation is greater than the value of the MOUNTLIMIT parameter for a device class, the transaction fails.

The following are possible values:

DRIVES: Specifies that every time a mount point is allocated, the number of drives that are defined and online in the library is used to calculate the true value.; Note: For EXTERNAL library types, do not specify DRIVES for the MOUNTLIMIT value. Specify the number of drives for the library as the MOUNTLIMIT value.
number: Specifies the maximum number of drives in this device class that are used concurrently by the server. This value must never exceed the number of drives that are defined and online in the library that services this device class.
0 (zero): Specifies that no new transactions can gain access to the storage pool. Any current transactions continue and complete, but new transactions are terminated.