After applying one hotfix to AX 2012 R2, the kernel version changed to 6.2.1000.986 and the application version is still the same 6.2.158.0.
I want to know is this behaviour is normal or am i missing anything here. Also I want to know the difference between application version and kernel version.
Is the hotfix a kernel hotfix? If yes then it is normal. However in few cases it happens that you upgrade to later roll-up version or install application hotfix and your application version does not change. You can go to the *\msi* folder of the roll-up/hotfix downloaded path and repair the ObjectServer32/ObjectServer64 msi file. Restart your AOS and launch AX client again.
The Dynamics AX Kernel is the component executing the X++ Application code. So the Kernel version is the version of the executable (Client, Server, Business Connectors) while the Application version is the version of the Dynamics AX “Business Logic” - the X++ Application code, Forms, Reports – everything in the AOT.