First I installed Oracle 19c in Docker container , enabled unified auditing, and created multiple pluggable databases:
export ORACLE_SID=ORCLCDB
cd $ORACLE_HOME/bin
#connect to root container
./sqlplus / as sysdba
CREATE PLUGGABLE DATABASE testpdb1 ADMIN USER admin1 IDENTIFIED BY dbpasswd1
FILE_NAME_CONVERT=('/opt/oracle/oradata/ORCLCDB/pdbseed', '/opt/oracle/oradata/ORCLCDB/testpdb1');
Pluggable database created.
CREATE PLUGGABLE DATABASE testpdb2 ADMIN USER admin2 IDENTIFIED BY dbpasswd2
FILE_NAME_CONVERT=('/opt/oracle/oradata/ORCLCDB/pdbseed', '/opt/oracle/oradata/ORCLCDB/testpdb2');
Pluggable database created.