There are situations where in-memory-replication falls short - example a data-center catastrophe.
In that case, since the session is not stored in the database, in-memory replication may not help.
In-memory is useful for its (lack of) setup costs. HADB is highly-available "database" on the
other hand. The former imparts you reasonable availability, the later guarantees cross-domain availability, if you undertake the setup costs.
Naming enterprise profile domain that way may have been a mistake since both cluster and
enterprise profile are suited for enterprise use. It's just the use that differs. If you have a site like
mlb, hadb might be overkill, and in-memory replication might just work fine.
Hope this helps (a bit more) :)
Kedar
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