Migration Considerations; Coexistence - IBM RS/6000 SP Handbook

Migration considerations

HACMP 4.3.1 on the SP requires AIX 4.3.3 (or later) and PSSP 3.2. You have
the following migration options:
Migrating from HACMP/6000 1.2, 2.1, or 3.1 to HACMP 4.3.1 involves taking
configuration snapshots, bringing down the cluster, reinstalling HACMP on all
nodes in the cluster, and bringing it back up again.
Migrating from HACMP 4.1, 4.2, or 4.3.0 to HACMP 4.3.1 also involves
reinstalling HACMP on all nodes in the cluster; however the version
compatibility function allows you to upgrade the cluster one node at a time
without taking the entire cluster offline.
Due to HACMP dependencies on levels of AIX, migrating one node at a time
might require you to upgrade AIX, PSSP, and HACMP on the node all during
the same service window.

Coexistence

HACMP 4.3 is not compatible with any of its lower level versions
a version compatibility function to allow HACMP 4.3 to coexist in a cluster with
HACMP 4.2 or HACMP 4.1, this function is intended as a migration aid only.
Once the migration is completed, each processor in the HACMP cluster must be
at the same AIX and HACMP release levels, including all PTFs.
418 RS/6000 SP and Clustered IBM ^ pSeries Systems Handbook
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