The bitmap can be used
For example, if you dismount
a three-member shadow set consisting of D1, D2, and D3, and you then
mount only D1 with the /POLICY=MINICOPY[=OPTIONAL] qualifier, a bitmap
is created. When you mount either D2 or D3 back into the shadow set,
a minicopy is performed. When you mount the remaining member into
the shadow set, a full copy is performed.
To avoid the requirement of a full copy on the
second member, dismount shadow set members one at a time, using /POLICY=MINICOPY
for each. In that way, you have a bitmap for each shadow set member.
When you return each disk to the shadow set, you can do a minicopy