I’ve gotten a few questions about this recently, so I decided to post a review of patching the weblogic server in EBS. When you are ready to patch the weblogic installation (on a test system, please). Make sure you are in a patch cycle and remember that you will need to to do an fs_clone phase after cutover.
Start with the quarterly patch set you wish to apply to WLS. There is no need to run ETCC at this time since the patches returned will change after the new PSU is installed. In this case, we will start with the April 2021 CPUs. This means that our master note is 2759182.1. From this we can determine that for WLS, we want to apply 10.3.6.0.210420.
We know that it is highly unlikely that we will be able to install this without removing patches, so go ahead and open note 1470197.1, which will allow us to determine the previous PSU.
Now go ahead and copy the jar and xml from the patch into place and attempt to apply (note you will probably need to adjust the memory settings in bsu.sh):
cp -p AXXI.jar patch-catalog_27497.xml $FMW_HOME/utils/bsu/cache_dir ./bsu.sh -install -patch_download_dir=$FMW_HOME/utils/bsu/cache_dir -patchlist=AXXI -prod_dir=$FMW_HOME/wlserver_10.3 -verbose
If this is not a new install, this is going to fail with a list of of patches that need to be removed, use note 1470197.1 to find the previous PSU in this list.
On my (rather old) test system, my initial list was Z9PC, YVDZ, YHJK, K25M, QMJP, EQDE, XNBA, KRDE, and 9KCT. From when I looked in note 1470197.1, I found that this system was on PSU 10.3.6.0.161018, K25M.
Frequently you can remove everything except the PSU in once pass, so you may find it worthwhile to try doing a single command to remove everything except the PSU, then remove the PSU, and then install the new PSU. You can do this as soon as you identify which patch in the original list is the current PSU.
./bsu.sh -remove -patchlist='Z9PC,YVDZ,YHJK,QMJP,EQDE,XNBA,KRDE,9KCT' -prod_dir=$FMW_HOME/wlserver_10.3 -verbose
If the remove fails, you can attempt to remove the old PSU (which will fail) in order to find out which if the patches are dependent on the PSU.
./bsu.sh -remove -patchlist=K25M -prod_dir=$FMW_HOME/wlserver_10.3 -verbose
Generally, you can then remove those patches, then the old PSU, then the rest of the conflicting patches.
./bsu.sh -remove -patchlist='EQDE,Z9PC,KRDE,9KCT,QMJP' -prod_dir=$FMW_HOME/wlserver_10.3 -verbose ./bsu.sh -remove -patchlist=K25M -prod_dir=$FMW_HOME/wlserver_10.3 -verbose ./bsu.sh -remove -patchlist='YVDZ,YHJK,XNBA' -prod_dir=$FMW_HOME/wlserver_10.3 -verbose
Now that the conflicting patches are removed, you can install the new PSU.
./bsu.sh -install -patch_download_dir=$FMW_HOME/utils/bsu/cache_dir -patchlist=AXXI -prod_dir=$FMW_HOME/wlserver_10.3 -verbose
After you have installed the new PSU, run the current ETCC (from patch 17537119) to find the additional patches you need for WLS and apply them. When you run ETCC, it will give you the current bundle patch that contains all of the patches that are needed on the middle tier. Hopefully most of these are already installed. For April 2021, ETCC also identifies a new BSU patch, 32898996. This is not in the April 2021 bundle patch, 32670837, and you will need to download and install it separately. Since ETCC just gives you the list of patches, be sure to read note 1594274.1 to make sure you follow any special instructions for the identified patches.
You can proceed to patch the rest of the middle tier products with the patches identified by ETCC. You can refer to note 1355068.1 for instructions on how to patch each of the web tier productions.
Note: When installing the ETCC patch, keep the current version you have installed until you have completed your cutover (similarly keep a copy of the older version on the database tier until you have patched it as well).