GETDUMP
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Syntax
GETDUMP dumpfile [ ldevlist ] GETDUMP dumpfile [ DIR ]This command is used to restore the contents of a tape created by the DUMP utility onto disk. Once restored, the dump must be opened by the OPENDUMP command for access by the DAT program. A tape request for dumptape is generated; a message appears on the system console informing the operator of the request. In order to conserve the disk space used to store a dump, DAT is capable of applying one of several data compression algorithms to reduce the required storage. Normally, DAT selects the algorithm which is known to produce the greatest compression, but other algorithms may be selected based on the setting of the environmental variable GETDUMP_COMP_ALGO. This variable may be set to a specific algorithm, or to the value "TAPE". This special setting instructs DAT to use the same algorithm used by DUMP when the tape was produced. While this setting may not result in minimal disk space consumption, it will optimize GETDUMP performance, since the dump tape data will never have to be recompressed with a different algorithm. Before data on a dump tape are copied to disk, DAT will preallocate a certain amount of disk space in order to avoid running out of this resource in the middle of a GETDUMP. The amount of space preallocated is controlled by the environmental variables DUMPALLOC_RLE and DUMPALLOC_LZ. One of these two variables will be used depending on the data compression algorithm applied to the dump disk file. See the ENV command for further information about the environmental variables mentioned above.
Parameters
- dumpfile
The name of the dump file to be created. Dump file names are limited to a maximum of five characters. All files related to the dump are given names composed of this name followed by a three-character mnemonic indicating the file contents.
- ldevlist
A list of secondary-store LDEVs to be read from the dump. If no list is given, all LDEVs on the dump are read.
- DIR
This option indicates that only the dump tape directory should be read and displayed, along with an estimate of the amount of disk space required to restore the dump. However, the dump itself is not restored. The use of the DIR option requires a dummy file parameter to be supplied, even though no disk files are created.
Examples
$nmdat > getdump examp dir
Please mount dump volume #1.
SA 2559 on KC (8/29/88 9:40)
Tape created by SOFTDUMP 99999X A.00.00
MPE-XL A.11.10 dumped on MON, AUG 29, 1988, 9:39 AM
Dump Tape Contents
------------------
PIM00 4.0 Kbytes
MEMDUMP 48.0 Mbytes
VM001 39.1 Mbytes
VM002 0.6 Mbytes
VM003 0.1 Mbytes
VM004 16.4 Mbytes
VM014 0.6 Mbytes
This dump will require approximately 62.1 Mbytes (#257913 sectors)
of disc space.
$nmdat >
The above example displays the directory of a dump tape and an estimate of the
amount of disk space required to restore the dump.
$nmdat > getdump examp
Please mount dump volume #1.
SA 2559 on KC (8/29/88 9:40)
Tape created by SOFTDUMP 99999X A.00.00
MPE-XL A.11.10 dumped on MON, AUG 29, 1988, 9:39 AM
Dump Tape Contents
------------------
PIM00 4.0 Kbytes
MEMDUMP 48.0 Mbytes
VM001 39.1 Mbytes
VM002 0.6 Mbytes
VM003 0.1 Mbytes
VM004 16.4 Mbytes
VM014 0.6 Mbytes
This dump will require approximately 62.1 Mbytes (#257913 sectors)
of disc space.
Please stand by for disc space allocation.
0 100%
Loading tape file PIM00 : +....+....+
Loading tape file MEMDUMP : +....+....+
Loading tape file VM001 : +....+....+
Loading tape file VM002 : +....+....+
Loading tape file VM003 : +....+....+
Loading tape file VM004 : +....+....+
Loading tape file VM014 : +....+....+
Please stand by while dump pages are posted to disk.
Dump disc file space reduced by 60% due to LZ data compression.
$nmdat >
The above example creates the dump file EXAMP. DAT keeps the user
informed as to how much of
the dump has been read in by printing a dot every time it transfers
10% of each file in the dump file from tape to disk. When the dump
has been fully restored, the amount of disk space saved due to data
compression is displayed.
Limitations, Restrictions
DUMP stores data on dump tapes in compressed form. Prior to DAT A.01.18, dumps were restored on disk in expanded form, possibly resulting in extremely large dump files. As of DAT A.01.18 and later versions, the GETDUMP command restores dumps in compressed form, often resulting in a significant savings in disk space when compared to uncompressed dumps. These versions of DAT are also able to access (with OPENDUMP) uncompressed dumps restored by previous DAT versions. GETDUMP always creates at least one file when restoring a dump, known as the MEM file. Its name is made up of the dump file name followed by "MEM". Uncompressed dump files use separate files for storing data dumped from secondary store (LDEVs) and Processor Internal Memory (PIM), while compressed dumps are usually restored entirely within the MEM file.
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