Sybase 12.4.2 manual Backup Examples, Other backup options, Waiting for Tape Devices, 388

Backing up your database

Other backup options

Specifying the block factor

Error checking

BLOCK FACTOR specifies the number of IQ blocks to write to the archive device at one time. It must be greater than 0, or BACKUP returns an error message. BLOCK FACTOR defaults to 25 on UNIX platforms. On Windows NT, the default BLOCK FACTOR is based on the block size of your database. For example, if the block size is 512 bytes, BLOCK FACTOR is 120 blocks. If the block size is 32KB, BLOCK FACTOR is 1 block.

This parameter also controls the amount of memory used for buffers during the backup, and has a direct impact on backup performance. The effects of the block factor are a function of disk subsystem speed, tape speed, and processor speed. Some systems have better backup performance with a smaller block factor, while others may have better backup performance with a larger one.

CRC ON or OFF activates or deactivates 32-bit cyclical redundancy checking on a per block basis. (BACKUP also uses whatever error detection is available in the hardware.) With CRC ON, the numbers computed on backup are verified during any subsequent RESTORE operation. The default is CRC ON.

Adding comments	WITH COMMENT specifies a string up to 32KB long as part of the header
	information for the backup archive. If you omit this option, BACKUP enters a
	NULL. You can view the comment string by executing a RESTORE
	DATABASE FROM CATALOG ONLY, or by displaying the backup
	log,backup.syb, that Adaptive Server IQ provides.
	If you need to back up an Adaptive Server Anywhere-only database, see the
	Adaptive Server Anywhere Reference Guide for additional BACKUP options.

Waiting for Tape Devices

During backup and restore operations, if Adaptive Server IQ cannot open the archive device (for example, when it needs the media loaded), it waits for ten seconds and tries again. It continues these attempts indefinitely until either it is successful or the operation is terminated with a CTRL-C.

Backup Examples

Example 1 — Full backup

This example makes a full, attended backup of the database asiquser to two tape devices on UNIX. Before running this backup you must position the tapes to the start of where the backup files will be written, and connect to asiquser. Then issue the following command:

BACKUP DATABASE

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