Those who know, it might seem very trivial what is the meaning of terms used by HDS to refer to various microcode releases. But when I tried to look up the meaning of them, mighty google failed, and had to ask our HDS support engineer to for more explanation. And here is how I understand it:
A code is either:
GA = General Availability – a code released to all customers
RGA = Recommended General Availability – Recommended by HDS to upgrade your arrays to if possible
MGA = Mandatory General Availability – Minimum you should have this in order to get full support
The sequence from most recent to oldest is – GA -> RGA -> Below RGA (BRGA) -> MGA -> BMGA.
If your array is BMGA, and you have an issue, the first thing they will ask is to bring it to MGA. Sometimes when a release has fixed lots of bugs, it becomes MGA bypassing RGA.
For AMS2100/2300/2500 as of 19/01/2012:
RGA and Higher: 08B5/K, 08B5/H, 08B5/F, 08B5/D
Below RGA: 08B5/B, 08B5/A, 08B3/B, 08B0/B, 08A0/J, and a few others
Below MGA: 0897/C, 0897/B, 0893/E, 0893/B, 0890/H, and a few others