Fairly simple one here - if you install AX2009/AX4 AOS on an AX2012 AOS machine the AOS performance counters get overwritten as they have the same name in all versions. For AX4/AX2009 this didn't really matter as there wasn't much difference in counters between the versions,  but in AX2012 there are additional counters so you really want to the AX2012 version to be the one in effect.

If this happens you can just re-register the AX2012 counters like this:

1. Stop any performance monitor collection logs that are using the Dynamics
AX perf counters.

2. Disable the existing counters. Run the following from an elevated cmd
prompt
lodctr /D:"Dynamics Server"

3. Unload the existing counters: unlodctr "Dynamics Server"

4.  Register the  new path to the AX 2012 AXPERF.DLL in registry

       (i) Browse to
[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\Dynamics
Server\Performance]

       (ii) Edit the reg key called "Library" and replace with following path
"C:\Program Files\Microsoft Dynamics AX\60\Server\Common\AxPerf.dll"

5. Load the counter registration information from AX 2012 bin folder of AX
Instance, e.g below we use the file from an instance called
MicrosoftDynamicsAX
lodctr "C:\Program Files\Microsoft Dynamics
AX\60\Server\MicrosoftDynamicsAX\bin\AX32SERV.INI"

6. You DON'T need to stop any AOS services. You can restart the perfmon
logging that was setup previously to use the AX 2102 counters. Or if you had an
interactive performance monitor window, in order to reload the new counters you
need to start a new performance monitor window

We're going to look at changing the name of the AOS performance counters for the next version so they won't get overwritten.