Attributes for 12000 MB 4 mm tape drives (self-configuring)

The following are attributes for 12000 MB 4 mm tape drives (self-configuring).

Block size

The IBM® 12000 MB 4 mm tape drive's throughput is sensitive to block size. The minimum recommended block size for this drive is 32 KB. Any block size less than 32 KB restricts the data rate (backup or restore time). The following table lists recommended block sizes by command:

Supported Command	Default Block Size (Bytes)	Recommendation
BACKUP	32 K or 51.2 K (default)	Uses either 32 K or 51.2 K depending on whether `Backup` is by name or not. No change is required.
TAR	10 K	There is an error in the manual that states a 512 KB block size. Set the Blocking parameter to -N64.
MKSYSB	See BACKUP	The MKSYSB command uses the BACKUP command. No change is required.
DD		Set the Blocking parameter to `bs=32K`.
CPIO		Set the Blocking parameter to `-C64`.

Note: You must be aware of the capacity and throughput when you select a block size. Small block sizes have a significant impact on performance and a minimal impact on capacity.

Device buffers: The general information for this attribute applies to this tape drive type.

Extended file marks: The general information for this attribute applies to this tape drive type.

Density setting #1 and density setting #2

The following chart shows the supported data cartridge type and density settings (in decimal and hex) for the IBM 12000 MB 4 mm tape drive. When you perform a restore (read) operation, the tape drive automatically sets the density to match the written density. When you perform a backup operation (write), you must set the density to match the data cartridge you are using.

Supported Data Cartridges	Native Capacity	Compressed Data Capacity	SMIT Density Setting	HEX Density Setting
DDS III	2.0 GB	4.0 GB	19	13h
DDS2	4.0 GB	8.0 GB	36	24h
DDS3	12.0 GB	24.0 GB	37	25h

Note: If you request an unsupported native capacity for the data cartridge, the drive defaults to the highest supported capacity for the data cartridge that is loaded into the drive.

Data compression: The actual compression depends on the type of data that is being written (see previous table). A compression ratio of 2:1 is assumed for this compressed data capacity.

Attributes with fixed values: The general information for this attribute applies to this tape drive type.