ERROR: ORA-44787: Service cannot be switched into. - 19c DB with R12.2.10

 Issue 

ERROR:

ORA-44787: Service cannot be switched into.

Sol:

QL> show con_name

 

CON_NAME

------------------------------

CDB$ROOT

SQL> alter pluggable database <PDNAME> close immediate;

 Pluggable database altered.

 SQL> alter pluggable database <PDNAME> open;

 Pluggable database altered.

You can then change the container without receiving this error.

SQL> alter session set container=<PDNAME>;

Session altered.