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Preparation Process
The following is a brief list of the preparation steps.
1. Decide which method you will be using to perform the backup. The
choice is dependant upon your specific hardware, media
configuration, and TurboSTORE product. Every option except single
requires a TurboSTORE product. The choices are:
Single Requires only one backup device. One file
at a time is stored. When the media (tape
or DDS) fills, the device rewinds the media,
you remove the media and replace it with new
media, and additional files are stored to
the new media.
Sequential Requires more than one backup device. One
file at a time is stored. One device is
used at a time. When the media (tape or
DDS) fills, additional files are stored on
the next device in line. You can set this
up to toggle between two devices, giving you
time to change media.
Parallel Requires more than one backup device. Files
are being stored to more than one device at
the same time. When the media is full on
one device, you remove the media and replace
it with new media, and additional files are
stored to the new media.
Parallel Pools Requires at least four backup devices.
Files are being stored to more than one
device at the same time. This is a
combination of Sequential and Parallel.
When the media (tape or DDS) fills,
additional files are stored on the next
device in line. You can set this up to have
multiple pairs of toggling devices.
2. Decide on the order that each backup device in the pool is to be
used.
3. Assign each device a position based on its logical device (LDEV)
number. Use the chart in Figure 3-1 as a tool to help you
assign your devices.
![[]](../../pic3k/M013445/FFN53c50.gif)
Figure 3-1. Multiple-Device Planning Chart
Selecting the Backup Method
The best way to use your backup devices depends upon the characteristics
of the files that you are storing, your needs for compatibility with
other versions of MPE, and your system configuration.
The characteristics of the set of files help determine choices (or
options) for storing them. Generally speaking, the more files in the
file set, the more it is to your advantage to use multiple devices. If
you are storing only a few files of moderate size, one backup device may
be sufficient. If you are storing many files (for example, all the files
in an account, or a smaller number of very large files), using a
multiple-device backup is probably to your advantage.
Your needs for compatibility with other versions of MPE limit your
choices. If you need to produce STORE backups that are compatible with
MPE V/E using the TRANSPORT parameter, you can only store files to a
single device. (See Appendix D, "STORE File Compatibility," for more
information on compatability.)
If you aren't limited by your need for compatibility with MPE V/E or
earlier versions of MPE XL, the most important determinant of which
multiple-device method to use is your system configuration. Use the
following the guideline to select a method:
* Which and how many backup devices do you have? Which devices you
may use for a multiple-device backup are described in Chapter 3,
"Preparing Storage Devices." Obviously, in order to use sequential
or parallel devices, you must have at least two backup devices.
If you have two or three devices, you may use either parallel or
sequential devices. If you have at least four devices, you may
begin to use two or more parallel device pools.
Selecting Backup Device Order
Once you've selected the method of multiple-device TurboSTORE/iX you want
to perform, decide on each backup device's order of use. Assign each
device a position based on its logical device (LDEV) number.
Use the chart in Figure 3-1 to help you assign your devices. Select
one of the TurboSTORE/iX methods in the chart, and then write in the LDEV
numbers of each device you plan to use in the order that you plan to use
it. For example, if you intend to use two parallel devices, write in the
LDEV number of the first device next to Device A and the LDEV number of
the second device next to Device B in the Parallel section of the chart.
It may be helpful for you to photocopy the chart and use it as a guide
whenever you use a multiple-device method to store files.
Assigning Device File Names
With TurboSTORE/iX, you can store files to several backup devices
sequentially or concurrently. When using multiple backup devices, you
have the choice of entering multiple FILE commands to assign a different
file name to each device or a single FILE command.
Assigning each device a different file name makes it easier to keep track
of each device's position in the backup media. When you receive media
requests, you know exactly to which device the request applies. You may
use LDEV numbers or a common device class in the FILE command. When you
use a device class to name backup devices, STORE asks you to assign a
logical device to the file name with a media request. Refer to Chapter
7, "Handling Media Requests" for more information. You must use LDEV
numbers to name devices if the devices are to be automatically allocated.
Assign unique file names based on each device's position in the backup.
For example, if you plan to use four parallel devices, you might issue
the following set of FILE commands:
:FILE BACKA;DEV=7
:FILE BACKB;DEV=8
:FILE BACKC;DEV=9
:FILE BACKD;DEV=11
Label sequential devices in order. For example, if you are using three
sequential devices, you might issue the following FILE commands:
:FILE BACK1;DEV=TAPE
:FILE BACK2;DEV=TAPE
:FILE BACK3;DEV=TAPE
Label parallel device pools both in parallel and sequential order. For
example:
:FILE BACKA1;DEV=7
:FILE BACKA2;DEV=8
:FILE BACKB1;DEV=9
:FILE BACKB2;DEV=11
If you issue a single FILE command when using multiple backup devices,
you assign a common file name and common device class to all of your
backup devices. For example:
:FILE T;DEV=TAPE
You use the common file name, T in the example above, to refer to each
device in your STORE command. In a media request, the system asks you to
assign an LDEV number to T for each device. If you have four backup
devices, you see four identical media requests. You assign a different
LDEV number to each media request based upon the order in which you
receive the requests. Refer to Chapter 7, "Handling Media Requests," for
more information.
Your FILE command gives the backup device a file name and identifies the
device. To store files to only one device, you backreference that device
in your STORE command, as described previously. For example:
:FILE T;DEV=TAPE
:STORE @.OPERATOR.SYS;*T
However, with TurboSTORE/iX you may choose to employ multiple device
configurations at times when you have a large set of files to store and
you want to speed up the process. If so, you probably want to use the
FILE command to give each device a file name that reminds you of its
position. Then use the STORESET parameter in a STORE command to
reference the multiple devices. For example, to store files to three
sequential devices, use the following set of commands:
:FILE SEQ1;DEV=7
:FILE SEQ2;DEV=8
:FILE SEQ3;DEV=9
:STORE @.@.@;;STORESET=(*SEQ1,*SEQ2,*SEQ3)
The above STORE command copies all system and user files to three
sequential devices. The parentheses surrounding backreferenced file
names group the devices into a device pool.
NOTE You do not backreference the file name of a backup device
immediately after the name(s) of the file(s) you are storing when
you use the STORESET parameter. Rather, you must use a placeholder
for the missing parameter normally supplied when using a single
backup device. The placeholder is provided by the use of ;; in the
STORE command.
If you gave the backup devices a single file name such as:
:FILE T;DEV=TAPE
enter the following STORE command to copy files to a set of three
sequential backup devices:
:STORE @.@.@;;STORESET=(*T,*T,*T)
To store files to a set of four parallel devices, you might use the
following set of commands:
:FILE PARA;DEV=7
:FILE PARB;DEV=8
:FILE PARC;DEV=9
:FILE PARD;DEV=11
:STORE @.OPERATOR.SYS;;&
:STORESET=(*PARA),(*PARB),(*PARC),(*PARD)
If you gave the backup devices a single file name such as:
:FILE T;DEV=TAPE
enter the following STORE command to copy files to a set of three
parallel backup devices:
:STORE @.@.@;;STORESET=(*T),(*T),(*T),(*T)
You describe parallel devices in the STORESET parameter by enclosing each
backreferenced device file name within parentheses. Use commas to
separate devices.
To store files to parallel device pools, use parentheses to group the
devices into pools. Separate the devices in the pool from one another
with commas. Commas also separate each device pool. For example, the
following commands copy files to two parallel device pools. Each device
pool contains two sequential devices. In the following example, STORE
uses a total of four devices divided into two device pools.
:FILE PPA1;DEV=7
:FILE PPA2;DEV=8
:FILE PPB1;DEV=9
:FILE PPB2;DEV=11
:STORE @.OPERATOR.SYS;;STORESET=(*PPA1,*PPA2),(*PPB1,*PPB2)
If you gave the backup devices a single file name such as:
:FILE T;DEV=TAPE
enter the following STORE command to copy files to a set of parallel
device pools:
:STORE @.@.@;;STORESET=(*T,*T),(*T,*T)