How would you upgrade SAP kernel 6.20 to 6.40 in an MSCS Environment on Windows 2003?
Proceed as follows:

Stop the SAP R/3 resource in the cluster. Leave the SAP disk online.

Replace the kernel in the executable directory. Don't forget the extra executables in the c:windowssapcluster or c:winntsapcluster (on both nodes) Start the SAP R/3 Resource in the Cluster again

All ABAP programs need to be re-compiled after the kernel upgrade to 6.20. Take the following steps to only recompile the ABAP programs in use;

To create a consistent status of ABAP sources and loads, proceed as follows:

Before the kernel upgrade, specify the available loads

• Call transaction SGEN and choose: Regenerate the available loads -> Continue -> Generate all objects with available load
• On the next screen, define the servers that should be included during the generation and choose 'Continue' The Job Monitor screen appears. Since the programs for which loads have already been generated are now stored in the GENSETC database table, you can exit transaction SGEN.

Perform the kernel upgrade
Start the SAP system with STARTSAP
Regenerate with the transaction SGEN.

• Call transaction SGEN and choose:
• Regenerate objects from last generation -> Continue -> Restart -> Select the servers -> Continue.
• Start the generation or schedule it. All the programs from which a load existed before the deletion now get a new load.