The DECram driver allows you to create a disk in physical memory and to read and write to that disk using standard OpenVMS disk I/O operations. This provides high-speed access to read-only data such as libraries, fonts, and command files. Additionally, the DECram disk can be used to hold temporary or scratch files that may be required by an application.


Other features include the following:

  • A DECram disk can be accessed through the OpenVMS file system in the same way physical disks are accessed, requiring no change to application or system software.
  • Using a DECram disk reduces I/O traffic by replacing disk I/O with main memory access. While the number of I/O operations does not change, the number of external disk read and write operations is reduced.
  • A DECram disk can be served in a OpenVMS Cluster configuration. The MSCP server implements mass storage control protocol software to make DECram disks accessible to all cluster members. For more information on served disks, refer to OpenVMS Cluster Systems.
  • A DECram disk can be a member of a host-based shadow set. Volume Shadowing for OpenVMS provides high data availability by duplicating data on multiple disks. If one disk fails, the remaining disk or disks can continue to service application and user I/O requests.

Software Requirements

  • Java 1.5.0 or later
  • Must be installed on an ODS-5 volume


  • On Integrity, DECnet is included in the Base Operating Environment.
  • On Alpha, DECnet is included in the ALPHA-LP license.