skip book previous and next navigation links
go up to top of book: HP OpenVMS System Manager's Manual, Volume 1:... HP OpenVMS System Manager's Manual, Volume 1:...
go to beginning of chapter: Managing Storage Media Managing Storage Media
go to previous page: Setting Up Disk Volume Sets Setting Up Disk Volume Sets
go to next page: Mounting ISO 9660 Volume Sets and GroupsMounting ISO 9660 Volume Sets and Groups
end of book navigation links

Expanding Volumes Dynamically   



Dynamic Volume Expansion (DVE), introduced in OpenVMS Version 7.3-2, allows you to explicitly expand a file system if its corresponding storage container has additional space and has been initialized for expansion. With Dynamic Volume Expansion, you do not need to take an application offline if that application suddenly needs more storage space. The file system expansion occurs while the application remains online.

File system expansion consists of the following steps:

  1. Reserve additional bitmap space on a disk.
  2. Enlarge your storage container.
  3. Dynamically expand a volume.

These steps are discussed in the following sections.

Reserving Additional Bitmap Space  

To expand your file system dynamically, you must first perform a one-time allocation of additional bitmap space. To do this, you allocate space to the maximum size that can ever be used on a volume; OpenVMS imposes an upper limit of 1TB.

You can perform the one-time allocation of additional bitmap space at either of the following times:

Once allocated, the volume can be expanded while the disk is mounted as shareable (MOUNT /SHARE).

Notes about using these commands:

Enlarging Storage Containers  

You can enlarge storage containers in either of the following ways:

Using Additional INITIALIZE Qualifiers for Dynamic Volume Expansion 

For better performance, you might want to create a file system that is smaller than the current physical size of the volume. If you have a 36 Gb disk, but you anticipate adding an 18 Gb disk in the future, you might initialize the disk with the INITIALIZE /LIMIT command and then enter the following command to reserve 18 Gb of bitmap space:

$ INITIALIZE /SIZE=18000000 $1$DGAnnn
This command initializes the disk at 18 Gb of file system space. You can expand the file system later, if the need arises.

To increase the expansion limit on volumes already in use, plan to increase the expansion limit during the next convenient maintainance period using the SET VOLUME /LIMIT command.

When you use the /LIMIT qualifier with the INITIALIZE or SET VOLUME command, you increase the BITMAP.SYS file by a few hundred blocks, which gives you much greater flexibility in the future. You can later expand the volume (using the SET VOLUME /SIZE command) quickly if your storage requirements increase unexpectedly.

Increasing the Expansion Limit of Volumes in a Cluster 

To increase the expansion limit of volumes in a cluster, do the following:

  1. Verify that all systems in the cluster are running OpenVMS Version 7.2 or higher.
  2. If the disk is mounted shareable (if you specified one of the following qualifiers when you mounted it: /CLUSTER, /GROUP, /SYSTEM, or /SHARE), dismount the disk and remount it for private use. Do not specify /CLUSTER,/GROUP, /SYSTEM, or /SHARE.
  3. Remount the disk as shareable.

The following example shows how to increase the expansion limit of a volume mounted in a cluster:

$ DISMOUNT /CLUSTER /NOUNLOAD $252$DUA716:
$ MOUNT $252$DUA716: TST716
$ SET VOLUME /LIMIT $252$DUA716:
$ DISMOUNT /NOUNLOAD $252$DUA716:
$ MOUNT /CLUSTER $252$DUA716: TST716

go to previous page: Setting Up Disk Volume Sets Setting Up Disk Volume Sets
go to next page: Mounting ISO 9660 Volume Sets and GroupsMounting ISO 9660 Volume Sets and Groups