I need to know if IDRC is switchable on 3490 Tapes (Mod. Cxx, E11)
connected via SCSI or Channel Emulator/A to an RS/6000. If yes,
is this also true for Tape Units installed in a 3494? How is this
done, via SMIT or by AIX commands?
ANSWER
The IDRC (or hardware compression) used on the 3490E model C11/C1A,
C22/C2A, E01 and E11 tape drives can be turned on or off via software
control if these drives are SCSI attached.
On the SMIT screen entitled "Change / Show Characteristics of a Tape
Drive", there are many options. For example:
Tape Drive rmt1
Tape Drive type A3490E
Tape Drive interface scsi
Description IBM SSD 3490E tape dev>
Status Available
Location 00-04-00-50
Parent adapter scsi1
Connection address 50
Block Size (0=Variable Length) .0. +#
Use DEVICE BUFFERS during writes yes +
Use Hardware Compression on Tape .yes. +
Use Autoloading Feature of ACL .yes. +
Allow Device to Dominate SCSI Bus Cycles .no. +
To change hardware data compression, you need to change the option
"Use Hardware Compression on Tape" to either yes or no, depending on
your need.
You may also execute the same command at the shell prompt via
chdev -l 'rmt1' -a compress='no'
Unfortunately, the channel attachment of these tape drives is done
via RPQ P83033, RISC System/6000 Parallel Tape Attachment/6000, which
is a different tape driver than the SCSI attach. We are unsure if the
same functionality exists in this driver. You may wish to contact
Steve Schwartz (ZAZSTEV at TUCVM2 for PROFS/OfficeVision notes) with
ADSTAR for more information.
Since the drives in the 3494 are either C1A or C2A, and they allow
both SCSI and channel attachment, then the SCSI attachment will have
the same abilities as listed above.
Please note: 3490E models C11, C1A, C22 and C2A can attach either via
SCSI, S/370 Channel or ESCON channel. The 3490E models E01 and E11
can only attach via a SCSI-2 Differential interface (either
Fast/Narrow or Fast/Wide).
S e a r c h - k e y w o r d s:
IRDC 3490 SMIT COMPRESS SWITCH
WWQA: ITEM: RTA000069704 ITEM: RTA000069704
Dated: 05/1996 Category: ITSAI6000HW
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