HP Integrity NonStop J-Series - Manual (Page 56)

One-time Synchronization
HP AutoSYNC User’s Guide—522580-017
3-18
Recovery
Recovery
While a replacement file is being transferred, AutoSYNC retains an existing destination
file by renaming it to a file named AAnnnnnn and placing it in a subvolume with the
MapDB name (normally ASYMAPDB) on the destination file set volume. Partitions,
alternate indexes and protection views are named ABnnnnnn, ACnnnnnn, and so on.
After the synchronization of a file is completed, the renamed recovery file, AAnnnnnn,
is purged unless a failure occurs. If the new file cannot be placed in the destination
location or a failure leaves the replacement file in a corrupt state, the saved version is
used to recover the file.
An archive index file named AAINDEX in the MapDB subvolume contains the mapping
of the original filename to the AAnnnnnn name.
This feature is controlled with the [AUTO]SYNCRECOVER global parameter. By
default, recovery is enabled. You can enable or disable recovery for a specific file set
or for a one-time synchronization by setting the RECOVERY attribute with ADD or
ALTER SYNCFILESET or specifying it as an option in the SYNCHRONIZE command.
Saved recovery files are purged when the replacement file has been transferred
successfully.
Recovery occurs immediately if the destination ASYSYNC process detects the failure
that would leave the file in a corrupt state. If, however, a cpu or media failure prevents
immediate recovery, any subsequent synchronization of the affected file sets will
perform the recovery.
BACKUP and RESTORE Programs
Private Copies of BACKUP and RESTORE
AutoSYNC makes use of the NonStop server’s BACKUP and RESTORE system
utilities. BACKUP is executed on the source system; RESTORE is executed on the
destination system.
In some operational environments, access to these programs is restricted. To use
AutoSYNC, you may need to obtain, license, and secure separate copies of BACKUP
and RESTORE.
You specify the alternate program names through the BACKUP and RESTORE
options.
Number of Files per BACKUP Process
BACKUP performance degrades significantly when the number of files is large. To
avoid performance degradation and limits in the BACKUP program, AutoSYNC
restricts the number of files it assigns to any one BACKUP process. AutoSYNC starts
multiple BACKUP processes, in sequence, to process all the files it is synchronizing.
The default number of files per BACKUP process is 1000.