IBM 000-8697 Manual Do Utilizador

Operating OnLine

If you change the pathname to /dev/null, the change proceeds more
smoothly if you make the change while OnLine is offline. If

TAPEDEV

 is set

to /dev/null, you cannot perform a restore.

The tape device specified by the pathname must perform a rewind before
opening and on closing.

If you are logged in as user informix, you can change the value of

TAPEDEV

from within

DB-M

onitor or from the command line. If you are logged in as

, you must use the command-line option.

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 ensure
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 cannot 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

TAPEDEV

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 archive tapes. If the physical characteristics of the archive 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

TAPEDEV

at the time of

the level-0 archive is unavailable when the restore begins.