Oracle Enterprise Manager Cloud Control 13.5 Installation on Oracle Linux 9 (9.7) raises libclntshcore.so.12.1 No such file or directory

 To test an upgrade from an existing Oracle Enterprise Manager Cloud Control 13.5 to 24ai, I've installed in our lab environment a fresh Oracle Enterprise Edition Database on Oracle Enterprise Linux 9 (with the latest dnf update it is a 9.7). 

As 13.5 is supported and certified on Oracle Enterprise Linux 9 and Red Hat Linux 9 from Release Update (RU) 22 on, I followed the following note EM 13.5: Steps To Install OMS 13.5 On RHEL/OL 9. I've ensured that all gcc, glib-devel, etc. things are installed, as this is NOT checked within the prerequisite checks of the installer. One package is not available in Linux 9 (compat-libpthread-nonshared-2.28-225.el8.x86_64) - I come to this a little bit later.

To install the 13.5 EMCC on Linux 9 means to make a software only installation first, patching omspatcher and opatch and afterwards install the three java patches and on top the RU29, using the bitonly option (and ignoring the warning about metadata). As far, as good. 

When everything is patched, one can start the Configuration, in my environment I needed to run the /u01/app/oracle/product/em135/sysman/install/ConfigureGC.sh script. 

This works well, unless the point where the OMS should be started.  Then you will run in an error. 

Well, I was aware, that this can happen, because of the missing package in Linux 9. Another Oracle Note exists telling us, what to do in that case: EM13c: 13.5 OMS Installation on RHEL/OL9 Fails at OMS Start "libclntshcore.so.12.1: cannot open shared object file". 

So I downloaded the patch 35775632, extracted the stubs tar and re-run /u01/app/oracle/product/em135/bin/genclntsh - everything went well. 

I re-tried the Start Oracle Management Service in the Installer UI, but I've got the same error. (If you need to look into the logfiles, try to start the OMS manually with emctl start oms - you will get an output of the location of the logfiles. don't forget to stop the OMS with emctl stop oms later, before you retry to start it with the installation UI)

Checking for the existence of the libclntshcore.so.12.1 (or any links), I've found one at the agents lib directory (which was installed together with the Oracle Management Server automatically). I needed to copy that to the lib directories /u01/app/oracle/product/em135/lib AND to the OHS lib directory. This is NOT mentioned in the Oracle Support KB!

After doing so, I was able to re-run the start process at the UI and now the Enterprise Manager Cloud Control 13.5 on Oracle Linux 9 is up and running.