From VSI OpenVMS Wiki
Jump to: navigation, search

A minicopy is a streamlined copy operation involving copying data from a shadow set to a returning member of this shadow set using a shadow bitmap. A bitmap tracks writes to a shadow set and is used to direct a minicopy operation when a shadow set memberis returned to the shadow set. Instead of copying the entire contents of a device, only the changed blocks, identified by the bitmap, are copied. Minicopy ensures that the data on a shadow set member, when returned to the shadow set, is identical to the data in the shadow set.

The minicopy feature was introduced in OpenVMS Version 7.3.

Preparing for Minicopy

To prepare a shadow set for minicopy, use /POLICY=MINICOPY on the DISMOUNT command. You can view the bitmap created with SHOW DEVICES/BITMAP or SHOW DEVICES/FULL. You need the LOG_IO privilege to create bitmaps.

Performing a Minicopy

When a shadow set member for which a shadow bitmap was created (see Performing a Minicopy) is returned to the shadow set with a MOUNT command, a minicopy is performed automatically. To guarantee that only a minicopy takes place, use the /POLICY=MINICOPY qualifier on the MOUNT command.

See also