UPDATE DEVCLASS (Update an LTO device class)

Privilege class

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

Parameters

device_class_name (Required)

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

LIBRary

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

LBProtect

Specifies whether logical block protection is used to ensure the integrity of data stored on tape. When LBPROTECT is set to READWRITE or to WRITEONLY, the server uses this feature of the tape drive for logical block protection and generates cyclic redundancy check (CRC) protection information for each data block written on tape. The server also validates the CRC protection information when data is read from the tape.

The following values are possible:

READWrite

Specifies that logical block protection is enabled in the server and the tape drive for both read and write operations. Data is stored with CRC information in each block. This mode affects performance because additional processor usage is required for Tivoli® Storage Manager and the tape drive to calculate and compare CRC values. The READWRITE value does not affect backup sets and data that is generated by the BACKUP DB command.

When the LBPROTECT parameter is set to READWRITE, you do not have to specify the CRCDATA parameter in a storage pool definition because logical block protection provides better protection against data corruption.

WRITEOnly

Specifies that logical block protection is enabled in the server and the tape drive for write operations only. Data is stored containing CRC information in each block. For read operations, the server and the tape drive do not validate the CRC. This mode affects performance because additional processor usage is required for Tivoli Storage Manager to generate the CRC and for the tape drive to calculate and compare CRC values for write operations. The WRITEONLY value does not affect backup sets and data that are generated by the BACKUP DB command.

No

Specifies that logical block protection is not enabled in the server and the tape drive for read and write operations. However, the server enables logical block protection on write operations for a filling volume that already has data with logical block protection.

Restriction: Logical block protection is supported only on IBM® LTO5 and supported LTO6 drives.

FORMAT

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

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.

When migrating all drives from Ultrium to Ultrium 2 devices:

• Delete all existing Ultrium drive definitions and the paths that are associated with them.
• Define the new Ultrium 2 drives and paths.

If you are considering mixing different generations of LTO media and drives, be aware of the following restrictions.

Table 1. Read - write capabilities for different generations of LTO drives

Drives	Generation 1 media	Generation 2 media	Generation 3 media	Generation 4 media	Generation 5 media	Generation 6 media
Generation 1	Read and write	n/a	n/a	n/a	n/a	n/a
Generation 2	Read and write	Read and write	n/a	n/a	n/a	n/a
Generation 3 1	Read only	Read and write	Read and write	n/a	n/a	n/a
Generation 4 2	n/a	Read only	Read and write	Read and write	n/a	n/a
Generation 5 3	n/a	n/a	Read only	Read and write	Read and write	n/a
Generation 6 4	n/a	n/a	n/a	Read only	Read and write	Read and write
1 In a library with a Generation 3 drive, all Generation 1 scratch volumes must be checked out, and all Generation 1 storage pool volumes must be updated to read-only. 2 In a library with a Generation 4 drive, all Generation 2 scratch volumes must be checked out, and all Generation 2 storage pool volumes must be updated to read-only. 3 In a library with a Generation 5 drive, all Generation 3 scratch volumes must be checked out, and all Generation 3 storage pool volumes must be updated to read-only. 4 In a library with a Generation 6 drive, all Generation 4 scratch volumes must be checked out, and all Generation 4 storage pool volumes must be updated to read-only.

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

Table 2. Recording format and default estimated capacity for LTO

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.
ULTRIUM	100 GB	Uncompressed format, using Ultrium cartridges
ULTRIUMC	See note 200 GB	Compressed format, using Ultrium cartridges
ULTRIUM2	200 GB	Uncompressed (standard) format, using Ultrium 2 cartridges
ULTRIUM2C	See note 400 GB	Compressed format, using Ultrium 2 cartridges
ULTRIUM3	400 GB	Uncompressed (standard) format, using Ultrium 3 cartridges
ULTRIUM3C	See note 800 GB	Compressed format, using Ultrium 3 cartridges
ULTRIUM4	800 GB	Uncompressed (standard) format, using Ultrium 4 cartridges
ULTRIUM4C	See note 1.6 TB	Compressed format, using Ultrium 4 cartridges
ULTRIUM5	1.5 TB	Uncompressed (standard) format, using Ultrium 5 cartridges
ULTRIUM5C	See note 3.0 TB	Compressed format, using Ultrium 5 cartridges
ULTRIUM6	2.5 TB	Uncompressed (standard) format, using Ultrium 6 cartridges
ULTRIUM6C	See note 6.25 TB	Compressed format, using Ultrium 6 cartridges
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 sequential access volumes that are categorized by 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.

To force the Tivoli Storage Manager server to determine the estimated capacity for the volumes that are assigned to this device class, specify ESTCAPACITY="".

For more information about estimated capacities, see Table 2.

PREFIX

Specifies the high-level qualifier of the data set 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 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. 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, setting this parameter to a low value (for example, two minutes) enhances 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. 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. 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.

DRIVEEncryption

Specifies whether drive encryption is allowed. This parameter is optional. Drive encryption is supported only for Ultrium 4, Ultrium 5, and Ultrium 6 drives and media.

Restriction: If encryption is enabled for a device class, and the device class is associated with a storage pool, the storage pool should not share a scratch pool with other device classes that cannot be encrypted. If a tape is encrypted, and you plan to use it on a drive that cannot be encrypted, you must manually relabel the tape before it can be used on that drive.

ON

Specifies that Tivoli Storage Manager is the key manager for drive encryption and allows drive encryption for empty storage pool volumes only if the application method is enabled. (Other types of volumes are not encrypted. For example, back up sets, export volumes, and database backup volumes are not encrypted.) If you specify ON and you enable another method of encryption, drive encryption is not allowed and backup operations fail.

Note: You cannot specify Tivoli Storage Manager as the key manager for drive encryption of WORM (write once, read many) media. (If you are using WORM media, you cannot specify DRIVEENCRYPTION=ON.)

ALLOW

Specifies that Tivoli Storage Manager does not manage the keys for drive encryption. However, drive encryption for empty volumes is allowed if another method of encryption is enabled.

EXTERNAL

Specifies that Tivoli Storage Manager does not manage the keys for drive encryption. Use this setting with an encryption methodology that is provided by another vendor and that is used with Application Method Encryption (AME) enabled on the drive. When you specify EXTERNAL and Tivoli Storage Manager detects that AME encryption is enabled, Tivoli Storage Manager does not turn off encryption. By contrast, when you specify ALLOW and Tivoli Storage Manager detects that AME encryption is enabled, Tivoli Storage Manager turns off encryption.

OFF

Specifies that drive encryption is not allowed. If you enable another method of encryption, backups fail. If you enable the application method, Tivoli Storage Manager disables encryption and backups are attempted.