In addition to the above options, the following options are
available with TurboSTORE/iX 7x24 True-Online Backup:
ONLINE
After a short attach period, files can be accessed and modified during
backup.
ONLINE=START ONLINE=END
Files can be accessed without interruption throughout the
backup.
LOGVOLSET
Allows you to specify what volumeset should be used for online backup
log files.
Store to Disk
Instead of writing to a tape or MO device, STORE can write
the backup to a disk file. Refer to Chapter 3, "Preparing Storage
Devices," for more information.
Using TurboSTORE/iX 7x24 True-Online Backup, you can back
up files and applications that need to be available most or all
of the time. TurboSTORE 7x24 True-Online Backup can perform two
different types of online backups:
Using the ONLINE option only:
The first type of online backup requires that all files being store
be close for write access when the backup first starts. This is the
type of online backup available on pre-MPE/iX 5.5 systems, when the
TurboSTORE/iX II with Online Backup products are used (product
numbers HP36388A or HP36398A). This type of backup is referred to in
this manual as an online backup.
Using the ONLINE=START or ONLINE=END options:
Using the new functionality of TurboSTORE/iX 7x24 True-Online Backup,
you can also do an online backup of files and applications without
requiring that files be closed for write access at any time during
the backup. This is referred to in this manual as a 7x24
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:
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.
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).
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.
When online backup begins, the shadow subsystem assigns each
file in the store fileset to a log file created on the same volume
where the file resides. Actual logging activity does not take place
unless the file is modified after the attach phase.
TurboSTORE saves the changes made to databases and files being
stored in special log files. These files can become quite large
when there is a lot of activity on the system. The LOGVOLSET
option allows you to specify which volume set
to use for the log files. You can use this feature with the log
file size summary statistics from previous backups to ensure that
there is enough disk space for the online backup log files. The
log volume set is specified as follows:
:STORE /;*tape;ONLINE;LOGVOLSET=volumeset
The amount of log space required is directly proportional
to the amount of modifications performed against the attached file.
Therefore, the more modifications made to an attached file, the
more log space required. In the worst case, the maximum amount of
log space required equals the sum of the space required for all
of the files being stored. By storing the heavily modified files
first, you reduce the amount of logging space required. Reducing
the amount of logging data written to the backup media will also
reduce the time required to restore the files.
As each piece of backup media is filled, logging is disabled
for the files that were stored on that media.
Use the ONLINE parameter of STORE to perform an online
backup. Before the STORE process is initiated, you must warn the users
to close all files to ensure that the files are both physically
and logically consistent. For example, the following message can be sent:
WARN @S;ONLINE BACKUP WILL BEGIN IN TEN MINUTES.WARN @S;PLEASE CLOSE YOUR FILES.
Begin the online backup by specifying the ONLINE parameter with the
STORE command. For example, the following illustrates the
STORE command for an online backup.
When online backup begins, all files not currently open for write are attached
to a log handler known as the shadow subsystem. Once the attach phase is
complete, STORE issues the following message to the console.
FILES LOCKED BY ONLINE STORE ARE NOW FREE FOR READ/WRITE/PURGE
This message is also written to $STDLIST if STORE is being run from a
session. After you receive the above message, the users are allowed read, write
and purge access to the attached files. Send your users a message telling them
they may resume their applications. For example:
WARN @S;ONLINE BACKUP HAS BEGUN.YOU MAY NOW RESUME YOUR APPLICATIONS.
The NOTIFY option (described earlier in this chapter) can
be used to automate this task.
If any files were still open at the time you started online
backup, you will receive the following message:
! NOT STORED: FILE OPEN FOR WRITE AT ATTACH
where the exclamation point ( ! ) is replaced by the actual
filename(s).
During the RESTORE process, the log file is used to reconstruct the
original contents of the files; that is, the way they appeared at
the moment they were attached during online backup.
NOTE: The ONLINE option cannot be specified with the
SPLITVS or TRANSPORT options.
TurboSTORE/iX 7x24 True-Online Backup saves the changes made
to databases and files being stored in special log files. These
files can become quite large when there is a lot of activity on the system.
The LOGVOLSET option allows you to specify which volume set
to use for the log files. You can utilize this feature with the
log file size summary statistics from previous backups to ensure
that there is enough disk space for the online backup log files. The
log volume set is specified as follows:
:STORE /;*tape;ONLINE;LOGVOLSET=volumeset
LOGVOLSET can be used during an online backup (ONLINE) or
a 7x24 true-online backup (ONLINE=START or ONLINE=END).
It has no effect when specified for a non-online backup.