Oracle RESTRICTED SESSION error
If alter system disable restricted session doesn't work it means that there are patch violations

Check the status with below command:

select * from PDB_PLUG_IN_VIOLATIONS;


If post steps did not complete properly then it will keep PBD's in restricted mode. Run the below steps:

sqlplus / as sysdba

shutdown immediate
startup upgrade
alter pluggable database all open upgrade;
quit
cd $ORACLE_HOME/OPatch
./datapatch -verbose


check the log, should be no errors

sql&gt; shutdown immediate
sql&gt;startup 
sql&gt; alter pluggable database all open;