DEFINE DEVCLASS (Define an LTO device class)

Privilege class

To issue the DEFINE DEVCLASS command, you must have the system privilege or unrestricted storage privilege.

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 LTO tape drives used by the device class. For information about defining a library object, see the DEFINE LIBRARY command.

DEVType=LTO (Required)

Specifies that the LTO device type is assigned to the device class.

Restrictions:

• IBM LTO-9 tape drives are supported. However, when a new tape volume is inserted into an LTO-9 tape drive, the drive must load and initialize the tape. Typically, the loading and initialization process can be completed in two hours, but the time can vary, based on several factors. The initialization process continues until the tape drive is ready. You cannot cancel the process. To avoid this issue, manually load the volumes into the tape drive in advance, before the tape drive is used by the server. To manually load the tape volumes, you can use the IBM Tape Diagnostic Tool (ITDT) or the IBM Storage Protect lbtest utility.
• IBM LTO-9 tape drives require the ULTRIUM9 recording format for the uncompressed mode and the ULTRIUM9C recording format for the compressed mode.

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.

Note: The LBProtection setting applies only to empty/scratch tapes in the storage pool after the first write operation is performed on these empty tapes. Once LBProtection value Yes is marked to these volumes, the UPDATE DEVCLASS command is unable to change on this LBProtection value to these volumes.

Users should not change the LBProtect value in the middle of tape usages. The LBProtect value can be changed to a volume only when this volume is returned to a scratch volume.

The default is NO.

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 IBM Storage Protect 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 IBM Storage Protect 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: Restrictions apply to logical block protection (LBP):

• At the LTO-5 level, LBP is supported only on IBM LTO-5.
• Starting with LTO-6 level, LBP is supported on IBM LTO-6, non IBM LTO-6 and their higher generation drives.

WORM

Specifies whether the drives use WORM (write once, read many) media. This parameter is optional. The default is No. The field can contain one of the following values:

Yes

Specifies that the drives use WORM media.

No

Specifies that the drives do not use WORM media.

Note:

1. To use WORM media in a library, all the drives in the library must be WORM capable.
2. You cannot specify IBM Storage Protect as the key manager for drive encryption of WORM (write once, read many) media. (Specifying both WORM=Yes and DRIVEENCRYPTION=ON is not supported.)

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. Instead, specify the format that the drives use.

• If you plan to upgrade all drives to Generation 4, 5, 6, 7, 8, or 9, you must delete all existing LTO Ultrium drive definitions and the paths that are associated with them. Then, you can define the new Generation 4, 5, 6, 7, 8, or 9 drives and paths.

• LTO-8 drives are unable to read LTO-6 media. If you are mixing LTO-6 with LTO-8 drives and media in a single library, you must partition the library into two libraries. One library must have only LTO-8 drives and media and the other must have LTO-6 drives and media.

• LTO-9 drives are unable to read Ultrium 7 and Ultrium M8 media. If you are mixing LTO-7 with LTO-9 drives and media in a single library, you must partition the library into two libraries. One library must have only LTO-9 drives and media and the other must have LTO-7 drives and media.

• LTO-10 drives support two types of tape media; Ultrium 10 and Ultrium 10 Premium (Ultrium 10P). Both tape types use the same formats: ULTRIUMA and ULTRIUMAC. LTO-10 drives can read and write only Ultrium 10 and Ultrium 10P tape media.

If you are considering mixing different generations of LTO media and drives, consider the following restrictions:

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

Drives	Generation 3 media	Generation 4 media	Generation 5 media	Generation 6 media	Generation 7 media	Generation M8 media	Generation 8 media	Generation 9 media	Generation A media
Generation 3 1	Read and write	n/a	n/a	n/a	n/a	n/a	n/a	n/a	n/a
Generation 4 1	Read and write	Read and write	n/a	n/a	n/a	n/a	n/a	n/a	n/a
Generation 5 1	Read only	Read and write	Read and write	n/a	n/a	n/a	n/a	n/a	n/a
Generation 6 1	n/a	Read only	Read and write	Read and write	n/a	n/a	n/a	n/a	n/a
Generation 71			Read only	Read and write	Read and write	n/a	n/a	n/a	n/a
Generation 82	n/a	n/a	n/a	n/a	Read and write	Read and write	Read and write	n/a	n/a
Generation 93	n/a	n/a	n/a	n/a	n/a	n/a	Read and write	Read and write	n/a
Generation A4	n/a	n/a	n/a	n/a	n/a	n/a	n/a	n/a	Read and write
1 If a storage pool volume can only be read by a tape drive, ensure that the attributes of the storage pool volume are set to read only. 2 LTO-8 drives have two media types: LTO-M8 media and LTO-8 media. Both media types are used only in LTO-8 tape drives. 3 With LTO-9 drives, you can read and write data to LTO-8 tapes but not to LTO-M8 media. 4 With LTO-10 drives, you can read and write data to LTO-10 and LTO-10P (LTO-10 Premium) tapes 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 the DRIVE option for a library that contains some drives that support recording formats superior to other drives.
ULTRIUM3	400 GB	Uncompressed (standard) format, using Ultrium 3 cartridges
ULTRIUM3C	See the note 800 GB	Compressed format, using Ultrium 3 cartridges
ULTRIUM4	800 GB	Uncompressed (standard) format, using Ultrium 4 cartridges
ULTRIUM4C	See the note 1.6 TB	Compressed format, using Ultrium 4 cartridges
ULTRIUM5	1.5 TB	Uncompressed (standard) format, using Ultrium 5 cartridges
ULTRIUM5C	Varied, as described in the note	Compressed format, using Ultrium 5 cartridges
ULTRIUM6	2.5 TB	Uncompressed (standard) format, using Ultrium 6 cartridges
ULTRIUM6C	Varied, as described in the note	Compressed format, using Ultrium 6 cartridges
ULTRIUM7	6 TB	Uncompressed (standard) format, using Ultrium 7 cartridges
ULTRIUM7C	Varied, as described in the note	Compressed format, using Ultrium 7 cartridges
ULTRIUM8	12 TB for LTO-8 media 9 TB for LTO-M8 media	Uncompressed (standard) format, using Ultrium M8 or Ultrium 8 cartridges
ULTRIUM8C	Varied, as described in the note	Compressed format, using Ultrium M8 or Ultrium 8 cartridges
ULTRIUM9	18 TB for LTO-9 media	Uncompressed (standard) format, using Ultrium 9 cartridges
ULTRIUM9C	Varied, as described in the note	Compressed format, using Ultrium 9 cartridges
ULTRIUMA	30 TB for LTO-10 media	Uncompressed (standard) format, using Ultrium 10 cartridges
	40 TB for LTO-10P media	Uncompressed (standard) format, using Ultrium 10P cartridges
ULTRIUMAC	Varied, as described in the note	Compressed format, using Ultrium 10 cartridges
		Compressed format, using Ultrium 10P cartridges
Note: If the format uses the tape-drive hardware-compression feature, depending on the effectiveness of compression, the actual capacity is varied.

ESTCAPacity

Specifies the estimated capacity for the volumes that are assigned to the 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.

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 the device class, the server uses this prefix to create the data set name. This parameter is optional. The default value 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, 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. The default value is 60 minutes. You can specify a number 0 - 9999.

Restriction: If the library that is associated with this device class is external (LIBTYPE=EXTERNAL), do not specify the MOUNTWAIT parameter.

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 are 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 service 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. The default is ALLOW. Drive encryption is supported only for LTO-4 and higher generation 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 IBM Storage Protect 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, backup 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 IBM Storage Protect as the key manager for drive encryption of WORM (write once, read many) media. (Specifying both WORM=Yes and DRIVEENCRYPTION=ON is not supported.)

ALLOW

Specifies that IBM Storage Protect 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 IBM Storage Protect 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 IBM Storage Protect detects that AME encryption is enabled, IBM Storage Protect does not turn off encryption. By contrast, when you specify ALLOW and IBM Storage Protect detects that AME encryption is enabled, IBM Storage Protect turns off encryption.

OFF

Specifies that drive encryption is not allowed. If you enable another method of encryption, backup operations fail. If you enable the application method, IBM Storage Protect disables encryption and backup operations are attempted.