Capacity Scaling And Segmentation - IBM TS3500 Introduction And Planning Manual

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 servo manufacturer's word 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 already written on the tape. The microcode keeps
track of the last appendable point on the tape by means of an overwrite-protection
pointer 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 leverages
this support by providing an interface and control mechanisms that allow an
application or system to manage as needed. The control and status mechanisms for
this can be found primarily in mode pages X'23' and X'24'. For more information,
see the IBM System Storage 3592 Tape Drive SCSI Reference.
The 3592 tape drives allow append operations to data already on WORM
cartridges, and allow 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 may not 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, and JC over a broad range of capacities. The effect of capacity scaling is to
contain data in a specified fraction of the tape. This yields faster locate and read
times. Alternatively, you can purchase economy tapes (the JJ or JK 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) very fast access, and
another 200 GB (186.26 GiB) segment for additional capacity. You can purchase 300
GB (279.39 GiB) data tapes that are pre-formatted in these segments, or you can
segment and capacity scale them at a later time. Segmentation is only available
within a specified range of capacity scaling settings. Capacity scaling is not
supported for economy or write-once-read-many (WORM) tapes. For information
176
IBM System Storage TS3500 Tape Library with ALMS: Introduction and Planning Guide