All:
Just completed some development environment upgrades to 14.10.FC7 (from FC6) and hit on a couple of issues you should be aware of.
First, as noted in other threads, the MIRROR parameter has been deprecated and the engine setting is now always on. So if you weren't previously using it and had left the MIRRORPATH to a default setting, you need to clear that field out or it's going to barf.
Second, we've got some microservice type processes that connect to our databases pretty aggressively, with fairly rapid retries. On two different instances, these processes constantly trying to connect somehow munged the SMI rebuild that happens as part of the upgrade process. This caused the engine to get stuck in single-user mode and the sysmaster database to be inaccessible. The workaround (for me) was to comment out DBSERVERALIAS and edit sqlhosts to change the port for DBSERVERNAME to an unpublished one before running the upgrade. You could also put a firewall block on the main port. Once I did this, the upgrade completed quickly and without incident.
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TOM GIRSCH
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#Informix