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z/VM toleration of Dynamic Volume Expansion

Updated: 12 Dec. 2007


z/VM provides toleration for Dynamic Volume Expansion, a new functional capability for the DS8000 series, announced October 23, 2007.

US Announcement letter: ENUS107-610

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What is Dynamic Volume Expansion ?

Dynamic Volume Expansion provides the ability to increase the size of a logical volume while it is online to a host system. Both a 3390-3 and 3390-9 can be expanded. If a 3390-3 is expanded past 3339 cylinders, the device type will be changed to a 3390-9. A 3390-9 can be expanded up to 65,520 cylinders. A SCSI LUN can be expanded up to the current supported size of 2,147,483,640 blocks.

z/VM toleration support was added with APAR VM64305 (PTF UM32231 for z/VM V5.3 and PTF UM32230 for z/VM V5.2).


Considerations for expanding a volume

The following items should be taken into consideration when expanding a volume:

  • The expanded space on the volume cannot be used by z/VM until the volume is varied offline and online.
  • If the volume expansion changes the device from a 3390-3 to a 3390-9, ICKDSF CPVOL FORMAT should be used to format the expanded space and ensure the allocation map is in the correct format for the new volume size.
  • If the volume is shared across systems using cross system extensions (CSE), XLINK FORMAT should be issued after the device has been varied offline and online to ensure the expanded cylinders are mapped on the CSE track on the volume. Otherwise, unpredictable results could occur.


z/VM V5.3 changes in support of Dynamic Volume Expansion

For z/VM 5.3.0, when an ECKD volume is expanded:

  • The following message will be sent to the operator:

    HCP2298I Device rdev is pending expansion. The new size will be cccccccc cylinders.
  • The expanded space on the volume cannot be used by z/VM until the volume is varied offline and online.
  • Before the volume is varied offline and online, the QUERY DASD DETAILS response will include the following line:

    PENDING EXPANSION DETAILS: DEVTYPE = 3390-0A, CYLS = 47229

    where the DEVTYPE contains the model which may or may not have changed and the CYLS contains the new size which will be used by CP once the device is varied offline and online.

For z/VM 5.3.0, when an SCSI LUN is expanded:

  • No message is sent to the operator
  • The expanded space on the volume cannot be used by z/VM until the device is varied offline and online.
  • Before the device is varied offline and online, the QUERY DASD DETAILS response will display the old size of the volume and the QUERY EDEVICE DETAILS response will include the following line:

    PENDING EXPANSION NUMBER OF BLOCKS: 147483640

    where the NUMBER OF BLOCKS is the new size which will be used by CP once the device is varied offline and online.


z/VM V5.2 changes in support of Dynamic Volume Expansion

For z/VM 5.2.0, when an ECKD volume is expanded:

  • The following message will be sent to the operator:

    HCP2298I Device rdev is pending expansion. The new size will be cccccccc cylinders.
  • The expanded space on the volume cannot be used by z/VM until the volume is varied offline and online.
  • Before the volume is varied offline and online, the QUERY DASD DETAILS response will include the following line:

    PENDING EXPANSION DETAILS: DEVTYPE = 3390-0A, CYLS = 47229

    where the DEVTYPE contains the model which may or may not have changed and the CYLS contains the new size which will be used by CP once the device is varied offline and online.

For z/VM 5.2.0, when an SCSI LUN is expanded:

  • No message is sent to the operator
  • The expanded space on the volume cannot be used by z/VM until the EDEVICE is deleted or cleared and redefined.
  • Before the device is varied offline and online, the QUERY DASD DETAILS response will display the old size of the volume.


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