Administrator's Guide
This section describes how ADSM selects files for the
following operations:
- Full and partial incremental backups
- Selective backup
- Archive
- Migration from a client node (hierarchical storage management)
Clients can choose to back up their files using full or
partial incremental backup. A full incremental backup ensures that
clients' backed-up files are always managed according to policies.
Clients should use full incremental backup whenever possible.
If the amount of time for backup is limited, clients may sometimes need to
use partial incremental backup. A partial incremental backup should
complete more quickly and require less memory. When a client uses
partial incremental backup, only files that have changed since the last
incremental backup are backed up. Attributes in the management class
that would cause a file to be backed up when doing a full incremental backup
are ignored. For example, unchanged files are not backed up even when
they are assigned to a management class that specifies absolute mode and the
minimum days between backups (frequency) has passed.
The server also does less processing for a partial incremental
backup. For example, the server does not expire files or rebind
management classes to files during a partial incremental backup.
If clients must use partial incremental backups, they should periodically
perform full incremental backups to ensure that complete backups are done and
backup files are stored according to policies. For example, clients can
do partial incremental backups every night during the week, and a full
incremental backup on the weekend.
Performing full incremental backups is important if clients want the
ability to restore files to a specific time. Only a full incremental
backup can detect whether files have been deleted since the last
backup. If full incremental backup is not done often enough, clients
who restore to a specific time may find that many files that had actually been
deleted from the workstation get restored. As a result, a client's
file system may run out of space during a restore process. See "Special Considerations: Enabling Point-in-Time Restore for Clients" for more information.
When a user requests a full incremental backup, ADSM performs the following
steps to determine eligibility:
- Checks each file against the user's include-exclude list:
- Files that are excluded are not eligible for backup.
- If files are not excluded and a management class is specified with the
INCLUDE option, ADSM uses that management class.
- If files are not excluded but a management class is not specified with the
INCLUDE option, ADSM uses the default management class.
- If no include-exclude list exists, all files in the client domain
are eligible for backup, and ADSM uses the default management class.
- Checks the management class of each included file:
- If there is a backup copy group, ADSM goes to step 3.
- If there is no backup copy group, the file is not eligible for
backup.
- Checks the mode, frequency, and
serialization defined in the backup copy group.
- Mode
- Specifies whether the file is backed up only if it has changed since the
last backup (modified) or whenever a backup is requested
(absolute).
- Frequency
- Specifies the minimum number of days that must elapse between
backups.
- Serialization
- Specifies how files are handled if they are modified while being backed up
and what ADSM does if modification occurs.
- If the mode is modified and the minimum number of days have
elapsed since the file was last backed up, ADSM determines if the file has
been changed since it was last backed up:
- If the file has been changed and the serialization requirement is met, the
file is backed up.
- If the file has not been changed, it is not backed up.
- If the mode is modified and the minimum number of days have not
elapsed since the file was last backed up, the file is not eligible for
backup.
- If the mode is absolute, the minimum number of days have
elapsed since the file was last backed up, and the serialization requirement
is met, the file is backed up.
- If the mode is absolute and the minimum number of days have not
elapsed since the file was last backed up, the file is not eligible for
backup.
When a user requests a partial incremental backup, ADSM performs the
following steps to determine eligibility:
- Checks each file against the user's include-exclude list:
- Files that are excluded are not eligible for backup.
- If files are not excluded and a management class is specified with the
INCLUDE option, ADSM uses that management class.
- If files are not excluded but a management class is not specified with the
INCLUDE option, ADSM uses the default management class.
- If no include-exclude list exists, all files in the client domain
are eligible for backup, and ADSM uses the default management class.
- Checks the management class of each included file:
- If there is a backup copy group, ADSM goes to step 3.
- If there is no backup copy group, the file is not eligible for
backup.
- Checks the date and time of the last incremental backup by the
client, and the serialization requirement defined in the backup
copy group. (Serialization specifies how files are handled if they are
modified while being backed up and what ADSM does if modification
occurs.)
- If the file has not changed since the last incremental backup, the file is
not backed up.
- If the file has changed since the last incremental backup and the
serialization requirement is met, the file is backed up.
When a user requests a selective backup, ADSM performs the following steps
to determine eligibility:
- Checks the file against any include or exclude statements contained in the
user include-exclude list:
- Files that are not excluded are eligible for backup. If a
management class is specified with the INCLUDE option, ADSM uses that
management class.
- If no include-exclude list exists, the files selected are eligible
for backup, and ADSM uses the default management class.
- Checks the management class of each included file:
- If the management class contains a backup copy group and the serialization
requirement is met, the file is backed up. Serialization specifies how
files are handled if they are modified while being backed up and what ADSM
does if modification occurs.
- If the management class does not contain a backup copy group, the file is
not eligible for backup.
An important characteristic of selective backup is that a file is backed up
without regard for whether the file has changed. This result may not
always be what you want. For example, suppose a management class
specifies to keep three backup versions of a file. If the client uses
incremental backup, the file is backed up only when it changes, and the three
versions in storage will be at different levels. If the client uses
selective backup, the file is backed up regardless of whether it has
changed. If the client uses selective backup on the file three times
without changing the file, the three versions of the file in server storage
are identical. Earlier, different versions are lost.
When a user requests the archiving of a file or a group of files, ADSM
performs the following steps to determine eligibility:
- Checks the files against the user's include-exclude list to see
if any management classes are specified:
- ADSM uses the default management class for files that are not bound to a
management class.
- If no include-exclude list exists, ADSM uses the default management
class unless the user specifies another management class. See the
user's publication for the appropriate client for details.
- Checks the management class for each file to be archived.
- If the management class contains an archive copy group and the
serialization requirement is met, the file is archived. Serialization
specifies how files are handled if they are modified while being archived and
what ADSM does if modification occurs.
- If the management class does not contain an archive copy group, the file
is not archived.
A file is eligible for automatic migration from a client node if it meets
all of the following criteria:
- It resides on a node on which the root user has added and activated
hierarchical storage management. It must also reside in a local file
system to which the root user has added space management, and not in the root
(/) or /tmp file system.
- It is not excluded from migration in the include-exclude list.
- It meets management class requirements for migration:
- The file is not a character special file, a block special file, a FIFO
special file (that is, a named pipe file) or a directory.
- The file is assigned to a management class that calls for space
management.
- The management class calls for automatic migration after a specified
number of days, and that time has elapsed.
- A backup version of the file exists if the management class requires
it.
- The file is larger than the stub file that would replace it (plus one
byte) or the file system block size, whichever is larger.
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