Converting EM Repository DB from Non-CDB to PDB

With EM 13.4 it is possible to use either non-CDB or a PDB as the repository database. This post shows the steps for converting a non-CDB EM repository DB to a PDB.
Main thing to look out for is that repository connection string is updated in various files the EM uses. Current connection string could be found out with the following command.
Mos Docs 2431726.1, 2144665.1 and 2214218.1 all mention the files where the connection string is specified. These are available in the following directories.
Main issue here is that connection string uses SID. Once the repos DB is plugged in as a PDB, the SID cannot be used to connect to it. Service name (SERVICE_NAME) must be used instead. Therefore as the first step the connection string would be updated to use service name instead of SID.
The current repos DB is called emandb1. It will have a default service called emandb1. The listener status command would give these details.

Service "emandb1" has 1 instance(s).
  Instance "emandb1", status READY, has 1 handler(s) for this service...

If the non-CDB is plugged as a PDB using the same name emandb1 then this will result in a default service for PDB called emandb1. This would allow OMS to connect to the PDB without requring any connection string change. Also changing the connecting string before non-CDB conversion would allow any connectivity related issues to be ironed out beforehand.
With this in mind change the connection string to use service_name instead of SID. First check the connection string with service_name works by using it on a sqlplus connection
Then use the following command (mentioned in 2214218.1, 1395107.1 and CC Advanced Installation and Configuration Guide) to change the connecting string. The documentation states to shutdown OMS before running this command. But it seems the admin server neeeds to be up for it to work. Good thing is comamnd will bring up the admin server.
Above shows the new connetion string uses service_name. Checking in individual files mentioned earlier, all but embi-policystoremerge-jpscfg.xml had the connection string changed correctly. The connectring string in file embi-policystoremerge-jpscfg.xml still refered to SID. Manually edit the connection string to use service_name. Once done login to cloud control and check all is working as expected. If any connectivity errors are there correct them before proceeding to next steps. The EM Repos DB target shown on the console may require re-discovering and promoting



Next step is to create a CDB to plug the repos non-CDB as a PDB. The repos DB has very specific requirements when it comes to their memory parametrs, redo log file sizes, hidden parameters and etc (refer earlier post). The simplest way to accomplish this is to create a template from current non-CDB and use the template to create a the CDB. Below two commands does exactly this.
The CDB is called emandb(different to current non-CDB repos DB name). The database created from template will have tablespaces that were created for EM repos use such as MGMT_AD4J_TS,MGMT_ECM_DEPOT_TS,MGMT_TABLESPACE. These could be dropped from the CDB to save space (alternatively edit the template so these are not created in the first place).
Next step is to plug the non-CDB as a PDB. For this test case used the manual method. Last set of steps are shown below. The non-CDB is plugged in as a PDB has the same name, emandb1.

SQL> CREATE PLUGGABLE DATABASE emandb1 USING '/home/oracle/emandb1_non_cdb.xml' copy;

Pluggable database created.

SQL> show pdbs

    CON_ID CON_NAME                       OPEN MODE  RESTRICTED
---------- ------------------------------ ---------- ----------
         2 PDB$SEED                       READ ONLY  NO
         3 EMANDB1                        MOUNTED
SQL> alter session set container=emandb1;

Session altered.

SQL> select name from v$datafile;
NAME
----------------------------------------------------------------------------------------
+DATA/EMANDB/A148AAC6957E5A34E0530500160A7405/DATAFILE/system.303.1082632693
+DATA/EMANDB/A148AAC6957E5A34E0530500160A7405/DATAFILE/sysaux.306.1082632693
+DATA/EMANDB/A148AAC6957E5A34E0530500160A7405/DATAFILE/undotbs1.304.1082632693
+DATA/EMANDB/A148AAC6957E5A34E0530500160A7405/DATAFILE/users.299.1082632693
+DATA/EMANDB/A148AAC6957E5A34E0530500160A7405/DATAFILE/oradbaudit.298.1082632693
+DATA/EMANDB/A148AAC6957E5A34E0530500160A7405/DATAFILE/mgmt_ad4j_ts.305.1082632693
+DATA/EMANDB/A148AAC6957E5A34E0530500160A7405/DATAFILE/mgmt_ecm_depot_ts.297.1082632693
+DATA/EMANDB/A148AAC6957E5A34E0530500160A7405/DATAFILE/mgmt_tablespace.307.1082632693

8 rows selected.

The new PDB now containes the datafiles related to EM related tablespaces. Complete the conversion with the following.

@?/rdbms/admin/noncdb_to_pdb.sql

SQL> show pdbs

    CON_ID CON_NAME                       OPEN MODE  RESTRICTED
---------- ------------------------------ ---------- ----------
         3 EMANDB1                        MOUNTED
SQL> alter pluggable database open;

Pluggable database altered.

SQL> show pdbs

    CON_ID CON_NAME                       OPEN MODE  RESTRICTED
---------- ------------------------------ ---------- ----------
         3 EMANDB1                        READ WRITE NO

Once the PDB is open the listener will have a service emandb1 (PDB default service) for emandb CDB instance.

Service "emandb" has 1 instance(s).
  Instance "emandb", status READY, has 1 handler(s) for this service...
Service "emandb1" has 1 instance(s).
  Instance "emandb", status READY, has 1 handler(s) for this service...

Use sqlplus with same connection string as before to check connectivity to the PDB.

sqlplus sysman@"(DESCRIPTION=(ADDRESS_LIST=(ADDRESS=(PROTOCOL=TCP)(HOST=console-srv)(PORT=2020)))(CONNECT_DATA=(SERVICE_NAME=emandb1)))"

If connectivity is fine start the OMS.

emctl start oms
Oracle Enterprise Manager Cloud Control 13c Release 4
Copyright (c) 1996, 2020 Oracle Corporation.  All rights reserved.
Starting Oracle Management Server...
WebTier Successfully Started
Oracle Management Server Successfully Started
Oracle Management Server is Up
JVMD Engine is Up

Discover the new EM repos db and related PDB targets and promote them. The dbsnmp common user in CDB will be in locked status. Unlock the dbsnmp account and give a new password.

The old EM repos db will be in down state while newly promoted CDB and PDB will be shown up state.
Once confident all is working as expected the old EM repos DB could be dropped.