7.1 Overview
SysWorks manages storage on disks and tapes using a num-
ber of objects. Those which are similar for all disks and tapes
include:
.
Device
.
Device Type
.
Media
.
Media Type
.
Volume
.
Volume Set
Objects shared by disks tapes and other objects include:
.
Equipment
.
Equipment Type
.
OpenVMS Device Type
Objects specific to tapes and removable disks include:
.
Pool
.
Save-set
.
Storage Model
.
System Job
Objects specific to disks include:
.
Logical Disk
.
Logical Sub-Disk
.
Shadow Set (RAID-0)
.
Stripe Set (RAID 1)
Other objects include:
.
Catalog
.
Journal
Standard operations include:
.
Archive
.
Backup
.
Recover
.
Report
.
Restore
7.1.1 Meta objects
Brief descriptions of these meta objects are given below. More
detailed descriptions are available in the SysWorks Model
Reference .
A device is a piece of computer hardware and as such is also
represented as equipment. Its includes information such as
location, serial number and supplier etc.
A device type is the model for a device and as such is also
represented an equipment type. Its description includes the
OpenVMS device type (not to be confused with the SysWorks
device type). SysWorks has a pre-installed list of all Digital
disk and tape devices supported by OpenVMS.
Disk or tape media is the actual disk, diskette, tape cartridge,
cassette or reel which is loaded into a device and initialized or
mounted. Note that for fixed disk drives, the media is present
inside the device. The media has a name or label which is
usually affixed to its outer packaging.
The media type is the model for some media. Particular
device types can use one or more media types and media
types can be used by one or more device types. For instance,
each newer model of a device type typically supports the me-
dia types of its previous models, although not always with the
same functionality. An example is the TK70 tape drive (de-
vice type) which can read and write TK70 tapes (media type)
while providing read only access to TK50 tapes (media type).
A volume is the information container placed on some me-
dia. A new media is initialized with a volume. Generally their
is a one to one correspondence between a media and a vol-
ume. As such the volume name and the media name are the
same. An exception to this model might be a software dis-
tribution package in which the same volume may exist on
multiple media. A tape volume may have an expiry date at
which it changes from the used state to the unused state.
A volume set is a set of two or more volumes which are
bound together to form a larger storage container than a sin-
gle volume. A volume set is referred to as a volume for most
discussions.
A logical disk is a set of broadly related data spanning one
or more disk volumes. For example SysWorks supports a
user logical disk and a Pathworks logical disk. A logical disk
is represented as a search list of logical sub-disks.
A logical sub-disk is a root directory on a disk volume
which is placed in the search list which constitutes a logical
disk.
A save-set is a special file created by a backup which con-
tains the files which were backed up. With tape media a tape
volume may contain one or more save sets. The last save set
on the tape may be continue onto another tape i.e. a save-
set may span two (or more) tape volumes. This practice is
discouraged since it complicates storage management. By
default, SysWorks creates one or more backup save-set for a
single backup oeration on a single tape volume.
A catalog is a list of the files placed in storage. When each
save-set is created, the backup utility produces a journal of
which files have been stored in the save set. SysWorks later
reprocesses this journal to add entries to the catalog. When a
tape volume is erased or reused (i.e. re-initilized), all file en-
tries belonging to all save-sets which were on the volume are
removed from the catalog. A catalog can be searched from a
number of perspectives including file name and type or ex-
tension, directory name, application environment, group or
user name, disk volume, disk device, save-set, tape volume
etc.
A pool is a set of media from which media can be selected.
Attributes include the default tape media name format (eg.
BCK###) and last used (eg. 000). When tape media are
added to a tape pool, the tape media name defaults to the next
unused name (eg. BCK001).
A storage model describes a backup which is used regularly
and is usually executed as a system job. Attributes include
expiry interval (eg. 10 days, 40 days, 366 days).
A system job is an operation performed on a regular ba-
sis. It includes frequency (eg. daily, weekly, monthly), start
window (eg. must start between 2am and 4am), finish win-
dow (eg must finish before 8am) etc. The operation can be
represented by a DCL command procedure or a storage
model.
7.1.2 Operations
Brief descriptions of the operations relating to storage man-
agement are given below. More detailed descriptions are
available in the SysWorks Object Model Glossary .
A backup makes copies of files onto removable media for
storage. With SysWorks each backup operation creates one
or more save-sets. Multiple save-sets are created when a
backup spans more than one logical data structure. An ex-
ample of this is when a disk volume is backed up - a disk
volume may have multiple logical sub-disks so one save-set
is created for each logical sub-disk. A backup may be based
around an appropriate object including:
.
Application environment
.
Database
.
Disk device
.
Disk volume
.
Environment
.
File
.
Group
.
Logical disk
.
User
An archive is a backup operation followed by a delete of all
the files which were backed up.
A recover operation brings back files from storage. Where
the files constitute a database, a roll forward may be used to
recover the latest data.
A restore operation brings back a total set of files from stor-
age. Where the files constitute a database, a roll backward to
the database state at backup may be used.