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Volume Shadowing and DECram?

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The Question is:

Our customer would like to use DECram to solve file IO-issues.  This in
 combination with volume shadowing to a physical disk, and in a cluster
 environment.  According to the SPD of DECram 3.0 this is possible: "In DECram
 Version 3.0, Volume Shadowing for
OpenVMS will support shadow sets composed of DECram devices and other disk
 class devices. Removal of the last non DECram device will cause the shadow set
 virtual unit to abort and become unavailable."
Nontheless: the SPD of Volume Shadowing contradicts this: "Compaq DECram
 virtual disks can be volume shadowed only with other DECram virtual disks."
My assumption is that the latter SPD is not up-to-date yes, or am I mistaken?
Are there any specific requirements towards the device used to shadow the
 DECram disk with a physical disk?  I assume that any supported disk with
 minimum the same number of blocks as the RAM device created will do?
Thanks in advance for your support
Peter de Proost - Presales consultant

The Answer is :

  This configuration is known to work and is regularly used within
  OpenVMS Engineering and at specific customer environments, but the
  lack of a mechanism to control the flushing of the DECram contents
  out to a physical disk volume means that the data on the DECram can
  potentially be lost in the event of the dismounting (dismembering?)
  of the virtual unit, and thus this configuration cannot be formally
  supported at present.

answer written or last revised on ( 16-JUL-2001 )

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