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

Chapter 7 123
TurboSTORE/iX 7x24 True-Online Backup
Consistent Backups
Consistent Backups
Even though database files generally constitute the largest part of any backup,
TurboSTORE/iX 7x24 True-Online Backup also backs up system and non-database files.
Since TurboSTORE allows changes to files during a backup, it establishes a close tie to the
file system to ensure physical and logical consistency.
Physical Consistency
Physical consistency is ensured by providing a snapshot of the fileset at a specific point in
time, specifically, at the sync point. This is adequate for files that are not "related" to other
files, and have no dependencies on changes to other files. This includes system files, some
flat files and any other files not associated with a database.
For KSAM XL files and files enabled for transaction management, TurboSTORE
guarantees that no partial transactions are included in the copy of the file stored on the
tape. This ensures that a consistent copy of the file is stored.
If Native Mode Message files are open during the sync point, TurboSTORE follows the
necessary steps to successfully imitate closing the file to ensure data integrity, physical
consistency, and recoverability.
User-mapped files are managed the same way they were with as TurboSTORE/iX II with
Online Backup. Whenever changes are made to a user-mapped file being stored by a 7x24
true-online backup, the entire file is copied to TurboSTORE's log files. However, if a
user-mapped file is left open for write access across the sync point, then TurboSTORE
captures the last known state of the file, which would either be at the last FOPEN, FCLOSE,
or FCONTROL 6. If TurboSTORE does not capture any of these events, the file is stored in
whatever state it was in when TurboSTORE opened the file, which may be inconsistent. A
warning message is printed for all user-mapped files open across the sync point.
NOTE Compatibility mode (CM) files, namely Circular (CIR) files, and Relative I/O
(RIO) files have internal buffer structures that cannot be logged by
TurboSTORE. If these files are open for write access during the sync point,
TurboSTORE captures their last known state, which is either since the last
FCLOSE or the last FCONTROL 6. A warning is issued for all CM files that were
open across the sync point.
Logical Consistency
In addition to physical consistency, TurboSTORE/iX 7x24 True-Online Backup also
guarantees logical consistency for databases. This is done by setting the sync point to occur
when all open transactions against the databases have completed. No new transactions
can start until the open transactions are complete, which is called
quiescing the
database.
Although any type of database can be stored by TurboSTORE, only TurboIMAGE and
ALLBASE/SQL databases are automatically quiesced using special database intrinsics.