DECRAM$HELP.HLB  —  CREATE  DISK
    Create or modify a virtual disk, memory disk, of a specified
    capacity in local private memory or Galaxy shared memory.

    Format

      CREATE DISK disk-name

1  –  Parameters

 disk-name

    The name of the memory disk that you want to create or modify.

    The disk name must begin with MD followed by a controller letter
    between A and Z followed by the disk number from 0 to 9999 for
    served devices such as MDC256. The non-served device number
    limit is 32767.

2  –  Description

    The CREATE DISK command creates or modifies a memory disk in
    local private memory or Galaxy shared memory The command can be
    further refined with the available qualifiers. The command
    can be entered from the VMS prompt or the DECRAM> prompt.

    Requires AUDIT, CMKRNL, SYSLCK, SYSPRV, and PHY_IO privileges.

3  –  Qualifiers

3.1    /CAPACITY

       /CAPACITY=blocks

    This qualifier is required. You must specify the size of the memory
    disk to create or modify in blocks (512 bytes). Capacity=0 will
    return the memory to the operating system.

3.2    /MEMORY

 	/MEMORY=type

    This qualifier is not required and defaults to local. LOCAL means
    create the memory disk in local private memory. SHARED means create
    the memory disk in Galaxy shared memory. Local memory can be accessed
    on only the node or instance where it resides. Shared memory can be
    accessed from any Galaxy instance that attaches to the shared memory.
    Shared memory requires VMS Galaxy software to be loaded and running.

3.3    /PERSIST

 	/[no]PERSIST

    This qualifier is not required and defaults to /PERSIST. It
    controls whether or not the disk is restored after a reboot.

    Note that /nopersist and /serve are mutually exclusive.

3.4    /SERVE

 	/[no]SERVE

    This qualifier is not required and defaults to /NOSERVE. It
    controls whether or not disk serving is available for the
    VMSCluster. When /SERVE is selected, the disk is MSCP
    served. Once a disk is selected /SERVE it cannot be selected
    /NOSERVE.

    Note that /nopersist and /serve are mutually exclusive. Also
    note that served device numbers cannot exceed 9999.

3.5    /ALLOCLASS

 	/ALLOCLASS=number

    This qualifier is not required and defaults to 99. It is only
    allowed for SHARED memory type disks. Note that associating a
    particular controller letter with a specific allocation class
    is valid for all time! All time means as long as the shared
    memory section exists or the MDRECOVER.DAT file exists. Selecting
    an allocation class equal to the node's allocation class for
    shared memory disks is not allowed.

3.6    /WRITEBUFFERED

 	/[no]WRITEBUFFERED

    This qualifier is not required and defaults to /NOWRITEBUFFERED.
    It is selected to help reduce write recovery time after a power
    fail or system crash. Application recovery techniques and OpenVMS
    Volume Shadowing can also be used to reduce write recovery time
    after a power fail.

3.7    /RAD

 	/RAD=stripe	(default)
 	/RAD=number
 	/RAD=home
 	/RAD=(,,,)

     This qualifier is not required and defaults to striping the
     memory disk across all available RADs for local and shared disks.
     It is only effective when RAD SUPPORT is enabled on the system.
     It is used to specify a single RAD (i.e., a number such as 2) for
     both local and shared memory, or a comma separated list of RADs
     for shared memory only. It can also be used to select the home RAD
     or to change from a single RAD to striping.

4  –  Examples

  1.  $ decram create disk mdf1111 /capacity=16777216 /memory=local -
                                   /serve /nopersist /rad=2

      This example creates an 8 gigabyte memory disk mdf1111 in local
      memory with an allocation class equivalent to the node allocation
      class. It is issued from the VMS prompt. It will not persist at
      the next reboot but disk serving to the VMScluster is enabled.
      If the system has RAD SUPPORT enabled then RAD 2 will be used
      to create the disk otherwise OpenVMS will pick the RAD(s).

  2.  DECRAM> create disk mda0 /cap=1000034 /mem=shared /rad=(0,1)

      This example creates memory disk $99$mda0 in shared memory RAD 0
      and RAD 1 with a size of 1,000,034 blocks and allocation class
      99. It is issued from the DECRAM> prompt. It will persist at the
      next reboot but disk serving to the VMScluster is not enabled.

  3.  DECRAM> create disk mdb0 /cap=10000 /mem=shared /alloc=13
      DECRAM> create disk mdb1 /cap=10000 /mem=shared /alloc=13

      $ init $13$mdb0 $13$mdb0
      $ mount dsa0: /shadow=($13$mdb0:,$13$mdb1:) $13$mdb0

      This example creates two 10000 block shared memory disks with
      allocation class 13. One of them is initialized and a VMS
      Volume shadow set is made from the two memory disks. The memory
      disks are not served to the cluster.

  4.  VMS Galaxy Instance 0

      $ decram create disk mdb0 /capacity=10000 /memory=shared
      $ init mdb0 mdb0
      $ mount /cluster mdb0 mdb0
      $ show device mdb0

        Device            Device    Error    Volume     Free  Trans Mnt
         Name             Status    Count     Label    Blocks Count Cnt
        $99$MDB0: (BANG)  Mounted       0     MDB0      9967     1   2

      VMS Galaxy Instance 1

      $ decram create disk mdb0 /capacity=10000 /memory=shared
      $ show device mdb0

        Device            Device    Error    Volume     Free  Trans Mnt
         Name             Status    Count     Label    Blocks Count Cnt
        $99$MDB0: (BIG1)  Mounted       0     MDB0      9967     1   2

      This example assumes a two instance VMS Galaxy with DECRAM V3
      installed on both instances. It creates two 10000 block shared
      memory disks with allocation class 99. One of them is created on
      instance 0 and the other on instance 1. The shared disk is
      initialized and mounted cluster-wide from instance 0. Note that
      if a shared disk has been created on each instance the
      "$ decram create disk" command is only necessary on one instance.
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