Re: HP-UX / Informix backup

It is technically possible to use ontape & tbtape to create a backup into a Unix disk file. Apart from the dangers of overwriting the file during 'tape changes' there are at least two other problems. Firstly - file size. The maximum physical file size in many Unix systems is about 2 Gigabytes - if you try to write to a file bigger than this the internal file pointer just wraps because the pointer cannot hold an offset larger than about 2Gb. This means that you must not tell ontape / tbtape that the 'tape' is larger than 2Gb. If the thing does wrap, you will get no errors or warnings, but the data is not recoverable. The exact maximum file size is not clear to me, last time I tried on Solaris it was just under 2 GB. Not knowing what the max size on your system is might lose you more than just your users data! Second - compression. When you archive the resulting files to tape, be very very careful how you do it. If any compression creeps in the data is not recoverable. Informix have always, in my experience, refused to state in writing that using tbtape / ontape to disk is supported. Some Informix staff say it is, some say it isn't. None who say it is have ever agreed to put it formally in writing - perhaps wisely. Onarchive was introduced an provides the backup to disk facility - onbar is better. Onarchive works fine, but has few friends...