Solution to ORA-29548: Java system class reported: release of Java system classes in the database (19.0.0.0.240116 1.8) does not match that of the oracle executable (19.0.0.0.240416 1.8)

When I was trying to drop and recreate a schema in my PDB, I received the following error:

drop user myuser cascade
*
ERROR at line 1:
ORA-00604: error occurred at recursive SQL level 1
ORA-29548: Java system class reported: release of Java system classes in the database (19.0.0.0.240116 1.8) does not match that of the oracle executable (19.0.0.0.240416 1.8)

This occured since I had cloned the database from a source with a lower CPU level. To correct the situation: shutdown the entire cdb

SYS@_container_name SQL> show con_name

CON_NAME
------------------------------
CDB$ROOT
SYS@_container_name SQL> shutdown
Database closed.
Database dismounted.
ORACLE instance shut down.

Start up the database in upgrade mode:

SYS@_container_name SQL> startup upgrade
Database mounted.
Database opened.
SYS@_container_name SQL> show pdbs

    CON_ID CON_NAME                       OPEN MODE  RESTRICTED
---------- ------------------------------ ---------- ----------
         2 PDB$SEED                       MIGRATE    YES
         4 pdb1                           MOUNTED

Open the pdb1 in upgrade mode, too:

SYS@_container_name SQL> alter pluggable database all open upgrade ;

Pluggable database altered.

SYS@_container_name SQL> show pdbs

    CON_ID CON_NAME                       OPEN MODE  RESTRICTED
---------- ------------------------------ ---------- ----------
         2 PDB$SEED                       MIGRATE    YES
         4 pdb1                           MIGRATE    YES

Run datapatch:

cd $ORACLE_HOME/OPatch/
datapatch -verbose

Shutdown the database, open normally:

SYS@_container_name SQL> startup
SYS@_container_name SQL> show pdbs

    CON_ID CON_NAME                       OPEN MODE  RESTRICTED
---------- ------------------------------ ---------- ----------
         2 PDB$SEED                       READ ONLY  NO
         4 pdb1                           MOUNTED
SYS@_container_name SQL> alter pluggable database all open;

Pluggable database altered.

SYS@_container_name SQL> show pdbs

    CON_ID CON_NAME                       OPEN MODE  RESTRICTED
---------- ------------------------------ ---------- ----------
         2 PDB$SEED                       READ ONLY  NO
         4 pdb1                           READ WRITE NO

You can now drop the user:

SYS@_container_name SQL> alter session set container="pdb1";

Session altered.

SYS@_container_name SQL> drop user myuser cascade;

User dropped.