Value 0 stands for not participating in memory sharing and is the default.
Value 1 stands for participating in memory sharing.
When you set GALAXY to 1 in a hard partition, OpenVMS instances will share memory between soft partitions within that hard partition. (You can run more than two soft partitions in a hard partition, and you might might not want to share memory among all of them.) Note that GALAXY specifies only if a node uses shared memory. You do not need to use the parameter to run multiple cooperative instances of OpenVMS; you do this by console setup of the configuration tree that you want.