Re: ontape and tape files

In article <D19970203T41644X4433@grizzly.asl-labs.bc.ca>, Brian Hampson <brian@asl-labs.bc.ca> writes >We're considering putting data on the end of our Informix backups (done by >ontape), using cpio. Does ontape lay down a specific number of tape >files? (correct eof marker?) Or is that database size and format >dependant? > >i.e. it would be nice to be able to issue an mt -f /dev/rmt/0n fsf X, >where X will get me to the end of the ontape stuff to start writing. > >Thanks, > >B. I have a client who has done the something similar. They set the tape device for archives (TAPEDEV paramater in onconfig) to the non-rewindable tape device. (E.g. /dev/rmt/2n). Ontape basically writes everything to the tape in one session so use mt -f /dev/rmt/0n fsf 1 to skip one session on the tape and there you are. PS It is a correct EOT marker (End of Tape) i.e. finish writing - there are no EOF (End of File) markers on tapes only an end of tape(or session marker). i.e the last place written to during an open/write/close session. Note also that this is COMPLETELY UNSUPPORT BY INFORMIX. ALSO IT MAY NOT WORK ON ALL PLATFORMS. When multiple sessions can be handled like this is very device driver/hardware dependent. In relaity only possibly the person who wrote the device driver + the hardware designer could give you a definitive answer. Note also non-reqind device means it does not automatically rewind when you close the device. Ontape which comes with online 7 will expect an explict rewind after closing the device hence this will fail. This is stated in the Informix-Online Dynamic Server Administrator's Guide, Volume 2 Version 7.1 Page 38-63 :- "Online Tape Devices Must Rewind Before Opening and on Closing. The tape device specified by TAPEDEV must perform a rwind before opening and on closing, OnLine requires this because of a series of checks that it performs before writing to a tape. When OnLine attempts to WRITE to any tape other then the first 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 assume the tape was rewound on closing and begins to write. Whenever OnLine reads attempts to READ a tape, it first reads the header and looks for the correct information. OnLine does not find the correct header information at the start of the tape if the tape device did not rewind on closing during the write process." Nuff said. -- David Williams