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Operating OnLine 3-19
Change Pathname of Logical Log Tape Device
If you are logged in as user informix, you can change the value of LTAPEDEV
from within DB-Monitor or from the command line. If you are logged in as
root, you must use the command-line option.
Preliminary Consideration
Tape devices must rewind before opening and on closing to be compatible
with OnLine operation. The reason for this is a series of checks that OnLine
performs before writing to a tape.
Whenever OnLine attempts to write to any tape other than the first tape in a
multivolume backup or archive, OnLine first reads the tape header to make
sure that the tape is available for use. Then the device is closed and reopened.
OnLine assumes the tape was rewound on closing and begins to write.
Whenever OnLine attempts to read a tape, it first reads the header and looks
for the correct information. OnLine does not find the correct header infor-
mation at the start of the tape if the tape device did not rewind on closing
during the write process.
Create a level-0 archive immediately after you change the value of
LTAPEDEV
to ensure a proper restore. This is done for two reasons.
First, the OnLine restore procedure cannot switch tape devices as it attempts
to read the logical log backup tapes. If the physical characteristics of the log
file tapes change during the restore, either because of a new block size or tape
size, the restore fails.
Second, the restore fails if the tape device specified as LTAPEDEV at the time
of the level-0 archive is unavailable when the restore begins.
Important: At the beginning of a restore, the OnLine configuration, including
logical log devices, must reflect the configuration as it was when the level-0 archive
was created.
To specify a logical log backup tape device on another host machine, use the
following syntax:
host_machine_name:tape_device_pathname:
The following example specifies a logical log backup tape device on the host
machine kyoto:
kyoto:/dev/rmt01