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CHAPTER 11 Backup and Data Recovery
387
• 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.
Specifying the size of
disk backups
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.
Specifying stacker
devices
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.
Specifying devices for
third party backups
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”.