[cisco-voip] Chaining CCM upgrades

[Mike Armstrong]

According to the Compatibility Matrix, the 3.3(3)->4.0(2a) path is an 
"additional tested upgrade" but not "standard support".   I'm not sure what 
the difference is, but I've been told that TAC won't support the shortcut. 
The only direect 3.3 upgrade to 4.1 is 3.3(4)->4.1(2), but elsewhere in the 
docs they point out that several 3.3(4) features don't transfer to 4.1(2).

In my case, it may be moot, since the 3.3(3)->4.0(1) upgrade is failing with 
one of those weird "The instruction at "0x1024f6e7 referenced memory at 
"0x00000000". The memory could not be "read"." errors.  TAC is initially 
mystified, but we're going to pursue it this morning.

As for the Subscriber, I don't see the need to maintain currency.  I'm 
proposing simply disassociating the subscriber from the cluster, upgrading 
the Publisher, and building a new Subscriber altogether when the Publisher 
is ready.  The database will synchronize at that time, just as it did when 
the cluster was first built.  There is no requirement to maintain service 
during the upgrade(s).