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NetBackup System Administrator’s Guide - Windows NT Server
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OTM Tab
The OTM tab applies to Microsoft Windows clients and contains properties
that define the behavior of Open Transaction Manager (OTM). NetBackup uses
this program to back up files, databases, and applications that are open or
active.
Open Transaction Manager does its job by establishing a point-in-time view of
the data on the drives containing files to be backed up. This view is called a
snapshot. NetBackup then backs up the selected files as they exist at the time
of the snapshot, regardless of file system activity. The snapshot is maintained
by using a cache mechanism to store changes that occur during the backup.
In addition to eliminating problems with busy files, Open Transaction Manager
keeps all relationships between files in the backup intact. For example, assume
that keywords in files A and B must be synchronized for an application to
work. Without Open Transaction Manager, if A is backed up but B is changed
before it is backed up, the two files are not synchronized after a restore and the
application will not work. With Open File Manager, all files are backed up as
they exist at a single point in time so relationships are maintained and these
problems cannot occur.
The following summarizes the sequence of events during a backup with Open
Transaction Management:
1. Before the backup begins, Open Transaction Manager waits for a quiet
period to occur when no writes are being performed on the drives that have
the data to be backed up. This wait is required to ensure that the file system
is in a consistent state.
You define the length of the quiet period with the Busy file wait setting. If a
quiet period of sufficient length does not occur within the time specified by
Busy file timeout, the backup proceeds without open transaction
management.
2. If a quiet period of sufficient length is detected, the Open Transaction
Manager performs the actions necessary to record the snapshot.
3. The backup now begins and NetBackup starts reading data from the client.
If an application requests a read or write during the backup, Open
Transaction Manager handles it as follows:
Write requests:
NetBackup 3.2 System Administrator's Guide for Windows NT
NetBackup 3.2 System Administrator's Guide for Windows NT
