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Introducing CONTIGVOL in VOLUTIL by Rajanarayanan Subbiah Commercial Systems Division Product Overview A new command, CONTIGVOL in the VOLUTIL utility, has been included in MPE/iX Release 5.0 to help you create the required number of contiguous free sectors on LDEV 1 for UPDATE to succeed, and also to create contiguous free space on any specific volume. This command can be executed only by users with CV capability.
NOTE CONTIGVOL is not meant to be used as a disk management or defragmentation tool.
The CONTIGVOL command moves extents within the volume or outside the specified volume (but within the volume set, volclass, or volume) subject to the restrictions placed on the files, to which the individual extents may belong. All the volumes in the volume set to which this volume belongs, must be mounted and online and DSTAT must indicate that the volumes in the volumeset are mounted in either a MEMBER or MASTER state. CONTIGVOL can be run online, but by its very nature, may cause "out of disk space" errors on the specified volume. When you run CONTIGVOL on any volume in the system volume set, it is recommended that there be minimum activity on the system. On private volumes, it is recommended that there be minimum file creation activity on the specified volume.
\ \ \ Important Details \ Please Read If your disk is too fragmented, CONTIGVOL may not be able to give you the amount of free space you need. The CONTIGVOL command does not guarantee that the required free space will be created.
CONTIGVOL has two modes of operation: VINIT-mode and BLOCK-mode. The specification of the SIZE parameter ensures block-mode. * VINIT-Mode If no SIZE is specified, CONTIGVOL operates in this mode. All file extents on the specified volume are then candidates to be moved. An attempt is made to move the extents to lower sector addresses on the same volume. This behavior is similar to the VINIT-cond on MPE V. If the UNRESTRICTED option is specified, then extents may be moved to other volumes in the volume set. _________________________________________________________________ NOTE It may be necessary to run CONTIGVOL in VINIT-Mode more than once until no more extents can be moved, to achieve better results. _________________________________________________________________ * BLOCK-Mode When the SIZE parameter is specified, CONTIGVOL tries to create a contiguous block of free space at least as large as SIZE, on the specified volume. In this mode, extents may be moved to higher or lower sector addresses as required. If the UNRESTRICTED option is specified, then extents may optionally be moved to other volumes in the volume set. It is better to determine in advance, the exact size of the contiguous free space required. _________________________________________________________________ NOTE Extents belonging to open files will not be moved. _________________________________________________________________ A different SIZE specification may result in entirely different results in terms of size of the largest contiguous free space. In both modes, the option TIMEOUT may be specified. This is the maximum wall time in minutes after which CONTIGVOL should terminate. This enables setting up jobs to be run for a specific number of minutes on a regular basis. CONTIGVOL can be aborted interactively with a CTRL-Y, or by a "break/Abort". A job running CONTIGVOL can be safely aborted. Related Information The SHOWUSAGE command in VOLUTIL can be used in conjunction with CONTIGVOL to display the extent information on a particular volume. SHOWUSAGE displays the sizes of free, permanent and transient sectors on a volume. User Interface The parameters supported by the CONTIGVOL command in VOLUTIL are described as follows: Syntax CONTIGVOL [VOL=]{[sname:] vname} [[SIZE=] sectors] [[TIMEOUT=] minutes] {ldev } [;TRANSIENTOK] [; UNRESTRICTED] Parameters The CONTIGVOL command currently takes 5 parameters. VOL The LDEV number or the name of the volume to be condensed. Required. SIZE The required contiguous free space in sectors. If this parameter is not specified, then it would try to move all extents in the volume to lower sector addresses much like VINIT-cond in MPE V, or to other volumes in the volume set, based on file restrictions, and the UNRESTRICTED option. The specification of this parameter determines whether the command operates in the BLOCK-mode or the VINIT-mode. Default: VINIT-mode, all extents are considered for a move. Optional. TIMEOUT The maximum wall time in minutes after which the command should terminate. If this parameter is omitted then the command runs to completion. Default: No Timeout. Optional. TRANSIENTOK Specifies that the contiguous chunk could include transient space (valid only for volumes in the mpexl_system_volume_set). This option is expected to be used if CONTIGVOL is run prior to an UPDATE on LDEV 1. Optional. Default: No transient. UNRESTRICTED Specifies that extents MAY be moved to other volumes in a volume set based on file restrictions. Default: Restricted to the same volume. Optional.
NOTE Extents will never be moved in such a way that they violate any of the Volume_set, Volume_class, Volume restrictions placed on the file to which they belong.
\ \ \ Important Details \ Please Read * Only one CONTIGVOL command can be executed at any time on the system. A second invocation on any volume would wait until the previous invocation completes. * Since the free space created by executing CONTIGVOL is not reserved by any means, it is your responsibility to ensure that there is minimal file (creation) activity on this volume set before, during and after (if the free space is needed for a specific reason) running this command.
Examples The following examples show the usage of the CONTIGVOL command and the different types of results. They also demonstrate the messages displayed under different scenarios. Example 1. You want to do a VINIT-cond like condense on LDEV 2, to create a large contiguous free space. __________________________________________________________________________________ | | | | | volutil: contigvol 2; | | | | *Verify: 863392 contiguous sectors available on ldev 2. Continue [Y/N] ?y | | Processing Labels on Ldev 3 ...... | | Processing Labels on Ldev 2 ...... | | Processing Labels on Ldev 1 ...... | | Percent Complete 20 | | Percent Complete 40 | | Percent Complete 60 | | Percent Complete 80 | | Maximum Contiguous Sectors Free 1229408 | | | __________________________________________________________________________________ Example 2. You are about to do an UPDATE and need to condense LDEV 1 to create the largest contiguous free space on LDEV 1. Extents may be moved to other volumes. _________________________________________________________________________________ | | | | | volutil: contigvol 1; unrestricted | | *Verify: 95392 contiguous sectors available on ldev 1. Continue [Y/N] ?y | | Processing Labels on Ldev 3 ...... | | Processing Labels on Ldev 2 ...... | | Processing Labels on Ldev 1 ...... | | Percent Complete 20 | | Percent Complete 40 | | Percent Complete 60 | | Percent Complete 80 | | Maximum Contiguous Sectors Free 229408 | | | _________________________________________________________________________________ Example 3. You try to create 1 million sectors of free space on LDEV 12. No extents may be moved out of this volume. CONTIGVOL returns an error indicating that there are less than 1 million sectors free (total) on that LDEV. _____________________________________________________________________________________ | | | | | volutil: contigvol 12 1000000 | | | | *Error: Required Sectors must be between 1 and max free on disk. (volutil 38 | | | _____________________________________________________________________________________ So you try the UNRESTRICTED option, to create 1 million contiguous free sectors on LDEV 12. Extents may be moved to other volumes in the volume set. ___________________________________________________________________________________ | | | | | volutil: contigvol 12 1000000; unrestricted | | | | *Verify: 203808 contiguous sectors available on ldev 12. Continue [Y/N] ?y | | Processing Labels on Ldev 14 ...... | | Processing Labels on Ldev 13 ...... | | Processing Labels on Ldev 12 ...... | | | | Number of Blocks Tried 1 | | Number of Extents Moved 93 | | Maximum Contiguous Sectors Free 1010352 | | Requested Contiguous Sectors 1000000 | | | ___________________________________________________________________________________ Example 4. You want 150000 sectors of contiguous space on LDEV 1 which may be comprised of transient or free space. Specify the UNRESTRICTED and TRANSIENTOK options. _________________________________________________________________________________ | | | | | volutil: contigvol 1 150000; unrestricted; transientok | | *Verify: 20800 contiguous sectors available on ldev 1. Continue [Y/N] ?y | | Processing Labels on Ldev 3 ...... | | Processing Labels on Ldev 2 ...... | | Processing Labels on Ldev 1 ...... | | | | Maximum Contiguous Sectors Free 20800 | | Maximum Contiguous Sectors Free 20800 | | Maximum Contiguous Sectors Free 33120 | | Maximum Contiguous Sectors Free 44864 | | Maximum Contiguous Sectors Free 36032 | | Maximum Contiguous Sectors Free 76080 | | Maximum Contiguous Sectors Free 160352 | | Number of Blocks Tried 8 | | Number of Extents Moved 133 | | Maximum Contiguous Sectors Free 160352 | | Requested Contiguous Sectors 150000 | | | _________________________________________________________________________________