Sybase 12.4.2 Manuale Utente

Backing up your database

 

Specifying the block 
factor

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.

Error checking

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.

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 C

TRL

-

C

.

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