Kernel upgrade is an easy process. 

Go to the SAP OSS Site :- 

http://service.sap.com/SWCenter-Main
   SAP R/3 
      SAP R/3 4.6C 
          Binary Patches 
                SAP KERNEL 4.6D 

Download the kernel programs in a temporary folder. 

Create a folder and copy the executables /exe/run/ then uncar the downloaded files and replace the executables. 

It is recommended to shutdown the R/3 database and all services including saposcol. 

Then restart your system. 
 

A couple of important points to remember are :-.

a) Always make a copy of the files you're going to replace. For e.g. Create a directory (oldkern) and copy all the old files 
    before replacing them (this helps when sometimes the new Kernel has problems, and you can revert it)

b) You have to shutdown SAP and the Database using the OLD kernel file. Again it is good practice to shutdown everything 
     first.
 

Refer to this OSS note which is pretty useful :-

102461 - Installation of 4.0B/40B_COM kernel with 4.0A/40B
 

How do I find out the current patch level in SAP R/3 4.7

You can use either of these two methods:

1: Follow the path 

System --> Status --> Component Information (The Magnifying glass button in the SAP System Data section) 

2: Use the Transaction code ---- spam

spam(Support package manager) --> package level
 

Steps to Start Your Database After Kernel Upgrade

Do these steps to start your database:

1. Open command prompt

2. Give command: SQLPLUS "/as sysdba"
If its giving message connected to idle instance then proceed:

3. Give command: startup open
If its giving error that database is already open, shut it down first. Then first check what database process is up and running.

4. Try stopping the database: shutdown immediate.

5. Follow step 3 again after shut down the database.

6. Exit from SQLPLUS

7. Run command on command prompt: R3trans -d
Check the results whether its still giving error or if it completed with 000 return code, then try starting SAP.

Follow the above steps.

SAP Upgrade and Installation
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