STORE and TurboSTORE/iX Products Manual (B5151-90003)

Chapter 6 115
STORE and TurboSTORE/iX Command Options
TurboSTORE/iX 7x24 True-Online Backup Options
true-online
backup
.
• The second type of online backup, referred to as a
7x24 true-online
backup
, lets you backup applications without requiring any files to be closed for write
access at any time during the backup.
This section describes how to perform the online backups using just the ONLINE option. For
information on performing 7x24 true-online backups, refer to Chapter 7.
Performing an Online Backup
At the time the online backup is started, all files must be closed for a brief period while
they are attached to the
shadow logging system. Shadow logging saves the "before
images" of file blocks when the records in the file block are modified during online backup.
The before images are stored on tape and are used by RESTORE to reconstruct the
original contents of the file.
How much time is required for the files to be closed depends upon how many files are being
stored. The range of time is usually from 1 to 30 minutes. Applications should be closed
during this attach period. Any files open for write access during this period are NOT
stored.
The shadow logging subsystem maintains the original state of the files as they appeared
when the online backup began. If an attached file is modified, the before image of the
portion (block) of the file being modified is saved in a log file. After the store process has
written the attached file to the backup media, it requests the logging information from the
shadow subsystem and appends the logged data, if any, to the end of the data file.
If an attached file is purged during the online backup, the system logically removes the
file, but does not physically remove it until it has been stored. Therefore, the backup
reflects the state of the system at the time STORE was initiated.
NOTE
1. The shadow logging operation can fail if there is not enough disk space.
Error messages are displayed for all files that fail to store due to lack of
disk space. However, the backup will NOT abort.
2. You must purchase TurboSTORE/iX 7x24 True-Online Backup (B5152AA)
to use the ONLINE option. This functionality is the same as was previously
available in TurboSTORE/iX II with Online Backup (HP36388A and
HP36398A).
3. Any Image databases being stored with the ONLINE option should be
closed for write access before the backup is started. If user logging is
enabled for the database(s), then the current log file should be closed when
the database is closed. Once the attach period has finished, the database
can be opened again. A new user log file should be started at this time.
Heavily modified files should be stored first. This is accomplished by specifying these files
first in the STORE command fileset list. By storing these files first, you reduce the system
overhead and the amount of logging information written to the backup media.