IBM TS4500, Introduction And Planning Manual

Page: 157 / 218

WORM cartridges are formatted at the factory and cannot be converted to data
cartridges. The WORM tape media are formatted differently than the standard
read/write media. One field in the manufacturer's servo track tape identifier on the
tape designates that the medium is WORM. In addition, the cartridge memory
(CM) has a WORM indicator byte in the cartridge type field. Both of these
conditions must be true for the drive to work with a WORM cartridge. If one
condition is true and the other is false, an
ATTN DRV - Invalid Cartridge
message
displays. When the drive senses that a cartridge is a WORM cartridge, the
microcode prohibits the changing or altering of user data that is already written on
the tape. The microcode tracks the last appendable point on the tape by an
overwrite-protection pointer that is stored in the CM. Statistical Analysis and
Reporting System (SARS) data can be written and updated on WORM tapes
because the SARS data is not in the user area of the tape.
Each WORM cartridge is identified by using a unique cartridge identifier (UCID)
that is permanent and locked, and which, provides another level of security for
data that must be maintained. This permanent locked information is stored in both
the cartridge CM and on the tape itself, and can also be associated with the unique
bar code volume serial (VOLSER) number.
Some records retention and data security applications require the WORM function
of tape data storage. This WORM function is accomplished on the 3592 tape drive
by a combination of microcode controls in the drive and a WORM tape cartridge.
Special tamper-proofing techniques and checking prevent WORM cartridges from
being transported to or from a data cartridge shell or cartridge memory and being
inadvertently processed as a read/write cartridge. The drive microcode provides
an interface and control mechanisms that allow an application or system to
manage as needed. The related control and status mechanisms for can be found
primarily in mode pages X'23' and X'24'. For more information, see the IBM 3592
Tape Drive SCSI Reference (GA32-0466).
The 3592 tape drive allows append operations to data already on WORM
cartridges, and allows overwrite of file marks and other non-data attributes to
provide application transparency. However, they do not allow data-overwrite
under any circumstances. Once full of data, WORM cartridges cannot be reused or
erased by the drive and must be physically destroyed or bulk degaussed to delete
data. For full tape application usage, certain trailer and label record overwrites are
allowed.
Capacity scaling and segmentation
The 3592 tape drive supports capacity scaling for tape cartridges of media types
JA, JB, JC, and JD over a broad range of capacities. The effect of capacity scaling is
to contain data in a specified fraction of the tape, which yields faster locate and
read times. Alternatively, you can purchase economy tapes (the JJ, JK, or JL media
type) to achieve this faster performance.
The 3592 J1A tape drive divides tape into longitudinal segments. Using this
capability, it is possible, for example, to segment 300 GB (279.39 GiB) data tapes
into two segments: one segment with 64.42 GB (60 GiB) fast access, and another
200 GB (186.26 GiB) segment for more capacity. You can purchase 300 GB (279.39
GiB) data tapes that are pre-formatted with these segments, or you can segment
and capacity scale them later. Segmentation is only available within a specified
range of settings for capacity scaling. Capacity scaling is not supported for
economy or write-once-read-many (WORM) tapes. For information about
Chapter 2. Planning
139