Sybase 12.4.2 manual 387

CHAPTER 11 Backup and Data Recovery

Specifying the size of disk backups

Specifying stacker devices

Specifying devices for third party backups

•For unattended backups with SIZE and STACKER specified, Backup tries to open the next tape. If there are no volumes available, or if you did not specify STACKER, you get an error.

Any additional tapes do not contain the header information needed for a restore, so you must be careful to mount tapes in order during the restore or your database could become corrupt.

On Windows NT, there are special requirements for the SIZE option on tape devices:

•The value of SIZE must be a multiple of 64.

•If you specify a SIZE that is not a multiple of 64, it is automatically rounded down to a multiple of 64.

•If you do not specify SIZE explicitly, it is automatically set to 1.5GB.

If you specify SIZE explicitly on any platform, and on NT even if you do not specify it explicitly, then if you run of space on a tape backup, you get an error and the backup fails.

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, either attended or unattended, specify SIZE if you need a maximum size other than the default of 2GB. When you omit SIZE for a backup to disk, BACKUP assumes that each disk file you name as an archive_device can be up to 2GB.

For example, if you specify one archive_device, a disk file called janfull, and you specify SIZE 200000 for a maximum 200MB file, but your backup requires 2GB, then BACKUP creates ten 200MB files: janfull.1, janfull.2,...janfull.10.

The STACKER option of the TO clause indicates that you are backing up to an automatically loaded multitape stacker device, and specifies the number of tapes in that device. When ATTENDED is ON and STACKER is specified, BACKUP waits indefinitely for the next tape to be loaded. All tapes in a given stacker device must be the same size.

Note Do not specify SIZE or STACKER if you are using a third party backup product, as size information is conveyed in the vendor_specific_information string. To specify this string, see “Performing backups with non-Sybase products”.

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