While trying to open one pluggable database, I got the following errors:
While installing Apex 20.1 in one PDB, and while being very close to the installation completion, the session fully stucked.
I restarted the database (the CDB), then I tried to open the PDB, but I got the above errors.
While searching for this error, I came to very similar issue:
Initially,I started the database in “upgrade” mode, then I checked the status of the installed components:
As you see from the above output, the Apex’s version is NULL. This is due to the in-completed Apex installation.
(Note that the above errors are not Apex-specific, and may happen with any other components).
First, we will de-install the Apex, while the PDB is in the upgrade mode:
Now, run the above query again, and ensure Apex is not there:
The last step is to close the PDB and open it again in the normal read write mode:
The PDB started normally without the above errors.
Now, I can proceed with the Apex installation again, as explained in my post: