implementing segmentation and capacity scaling, refer to the README files that
pertain to your device driver at Fix Central.
For more technical information about WORM, capacity scaling, and segmentation,
see also the IBM 3592 Tape Drive SCSI Reference.
All TS1120 and later tape drives also support multiple format options, such as
scaling and segmentation modes that trade capacity for improved access times.
While 256 settings of the Capacity Scaling byte (and resulting fractional capacities)
are supported on these drives, the following three primary settings are
recommended for use:
v Full capacity default mode
v 20% scaled fast access mode (20% capacity that is scaled, front of tape used). The
Capacity Scaling byte is x'35'.
v Performance scaling for 87% capacity and a segmented format with recursive
accumulating backhitchless flush (RABF) capability (a non-volatile caching
technique) for the full cartridge. For WORM firmware for the 3592 tape drive,
the Capacity Scaling byte is x'E0'.
These settings are fully certified and are available as labeled and initialized
part-numbered cartridges. For the exact Mode Select commands and settings that
are necessary to invoke scaling, see the IBM 3592 Tape Drive SCSI Reference.
Scaling support in drive
Capacity scaling in the TS1120 and later tape drives is controlled by the host
program that performs a Scaling operation. The Scaling operation uses the
Capacity Scaling byte and the Capacity Scaling Valid control bit in Mode page
X'23'. These tape drives do not change their current cartridge scaling, except for a
special condition. The drives change scaling when a SCSI Mode Select command
that specifies Mode Page X'23' (with appropriate non-default parameter settings) is
received while the cartridge is positioned at the beginning of the tape. The drive
can sense and report the scaling state of the current medium by using a Mode
Sense command that specifies Mode Page X'23'. The default unscaled capacity is
300 GB (279.39 GiB) for a JA cartridge in J1A density, 500 GB (465.66 GiB) for a JA
cartridge in E05 density, 700 GB (651.93 GiB) for a JB cartridge in E05 density, and
1 000 GB (931.32 GiB) for a JB cartridge in E06 density. The default unscaled
capacity for a JY cartridge in E07 density is 4 TB (3.64 TiB).The default unscaled
capacity for a JZ cartridge in E08 density is 10 TB (9.1 TiB).
v The cartridge can be rescaled from any current Capacity Scaling byte value to
any supported new value. The tape is logically erased by this (End of Data mark
that is written at beginning of tape), but not physically erased as with the long
erase command. Scaling or rescaling one cartridge does not cause rescaling of
the next cartridge; an explicit command must be issued for each cartridge to be
rescaled.
v The drive provides the option of setting the scaling values of N/256ths of full
capacity, where N ranges from X'16' (22 -- equals about 8% capacity) to X'EC'
(236 -- equals about 92%).
v For scaling factors N, between X'4B' and X'EB', the drive scales to the specified
amount and creates a fast-access 20% capacity segment in the beginning of the
scaled region.
v At all scaling factors, the drive supports early warning at the end of the scaled
region (with the appropriate unit attention to inform the software that it flushes
140 IBM TS4500: Introduction and Planning Guide
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