Sybase 12.4.2 manual 386

Backing up your database

Specifying tape devices on Windows

NT

Specifying the size of tape backups

Windows NT systems do not specify rewind or no rewind devices and only support fixed-length I/O operations to tape devices. Adaptive Server IQ requires variable-length devices. It does additional processing to accommodate NT’s fixed-length tape I/O.

While Windows NT supports tape partitioning, Adaptive Server IQ does not use it, so do not use another application to format tapes for Adaptive Server IQ backup or restore. Windows NT has a simpler naming strategy for its tape devices, where the first tape device is ’\\.\tape0’, the second is ’\\.\tape1’, and so on.

Warning! For backup (and for most other situations) Adaptive Server IQ treats the leading backslash in a string as an escape character, when the backslash precedes an n, an x, or another backslash. For this reason, when you specify backup tape devices you must double each backslash required by the NT naming convention. For example, indicate the first NT tape device you are backing up to as ’\\\\.\\tape0’, the second as ’\\\\.\\tape1’, and so on. If you omit the extra backslashes, or otherwise misspell a tape device name, and write a name that is not a valid tape device on your system, Adaptive Server IQ interprets this name as a disk file name.

For more information about fixed-length I/O on NT, see “Tuning backup operations” in the Adaptive Server IQ Installation and Configuration Guide.

The SIZE option of the TO clause identifies the maximum size of the backed up data on that stripe, in KB.

If you use the Sybase–provided backup (as opposed to a third party backup product), you should specify SIZE for unattended tape backups on platforms that do not reliably detect the end-of-tape marker. No volume used on the corresponding device can be shorter than this value. Although IQ does not require you to specify SIZE for an attended tape backup, it is always best to supply an accurate size estimate.

If tapes run out of space and you have not specified SIZE, you get an error. If tapes run out of space before the specified size, you do not get an error immediately; instead, here is what happens:

•For attended backups with SIZE and STACKER specified, Backup tries to open the next tape.

•For attended backups with SIZE specified but not STACKER, Backup asks you to put in a new tape.

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