SHADOW SYS DISK
SHADOW_SYS_DISK is a system parameter that enables (1) and disables (0) shadowing of the system disk. A value of 0 disables shadowing of the system disk. The default value is 0. Also specify a system disk shadow set virtual unit number with the SHADOW_SYS_UNIT system parameter, unless the desired system disk unit number is DSA0. A value of 4096 enables CI-based minimerge. To enable minimerge on a system disk, however, you must enable DOSD by setting the DUMPSTYLE parameter to dump off system disk, as described in the VSI OpenVMS System Manager's Manual. You can then add the value 4096 to your existing SHADOW_SYS_DISK value. For example, if you have SHADOW_SYS_DISK set to a value of 1, change it to 4097 to enable minimerge.