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, 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. See your platform operating system documentation for information about your platform’s optimal I/O size and block factor.
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 checksums computed on backup are verified during any subsequent RESTORE operation. The default is CRC ON.
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 Sybase 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.
