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Mixed Media Management
When the tape cartridge is unloaded, as part of the unload routine, the memory-
resident MIR information is written to the tape-resident MIR and the MIR invalid flag
is turned off. A copy of the memory-resident MIR is stored in the drive's persistent
memory (EEPROM) and used should the MIR fail to be written because of a power
failure or firmware problem (SNO or should not occur).
Cross-Density MIR Processing
Whenever a data cartridge is loaded that was written in a data density format that is
different from the one used when the drive writes, model-specific MIR processing
occurs. The following explanations cover:
• T9840D tape drive loaded with a lower-density cartridge
• T9840C tape drive loaded with aT9840D-written data cartridge
• T9840C tape drive loaded with a T9840A/B-written data cartridge
• T9840A/B drive loaded with a high-density tape cartridge
T9840D Tape Drive Loaded With a Lower-Density Cartridge
When the T9840D drive detects that a data cartridge is loaded, the drive first looks in
the designated location for a T9840D MIR. If a T9840D MIR is not found, the drive
then checks for a T9840C MIR and if its not found, it then checks for a T9840A/B
MIR. The processing for these operations is described in the sections below. If the
MIR cannot be read, the T9840D drive attempts to recover its contents using any
portions of the MIR that can be read and the contents of the Format Identity Burst
(FIB).
The T9840D drive uses a memory-resident copy of the MIR to access user data
pointers for read-only functions. Statistical counters are continuously updated in the
memory-resident MIR with any drive activity.
When the data cartridge is unloaded, the T9840D drives writes the FIB to the high-
density MIR location.
Notes:
• When the T9840D drive identifies the data cartridge as a low-density data
• The T9840D tape drive cannot correct or cause an invalid MIR on a T9840C
• The T9840D tape drive cannot correct or cause an invalid MIR on a T9840A/B
26 T9840 URM
Note – The FIB is written in a format that can be read by T9840C
and T9840A/B drives if they have an appropriate level of
firmware.
format, that is written by a T9840C or T9840A/B, Ready L appears on its
operator panel.
written data cartridge. A T9840C MIR can only become invalid during a mount
on a T9840C drive.
written data cartridge. A T9840A/B MIR can only become invalid during a
mount on a T9840A/B drive.
December 2012
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