12c clone PDBs in parallel

In one of the 12c Features presentation, one of the questions asked was if a Clone of PDBs can run in parallel ?

I.E, are there any locks held that will serialize creation of cloned PDBs. 

To clone a PDB in 12c, the procedure is to make the source PDB in read only mode, or use SEED database which is always in read only mode, i was fairly certain that no locks will be held. Still, to rule out any doubt, i ran a simple test. I created 5 PDBs in 5 different sessions at the same time. I noticed that all the PDBs were created at the same time proving that they can be created in parallel. 

The top wait event was "Pluggable Database file copy" of  "User I/O"  wait class while PDBs were being created.

below is the test script and the output.

[oracle@localhost pdbtest]$ cat a.sh
echo " starting PDBS at  $(date)"
for i in {1..5}
do
   echo "Welcome $i times"
  rm -r /home/oracle/pdbtest/$i
   mkdir /home/oracle/pdbtest/$i
   /home/oracle/pdbtest/b.sh $i &
done
wait
echo " Ending  PDBS at  $(date)"
[oracle@localhost pdbtest]$ 

[oracle@localhost pdbtest]$ cat b.sh

sqlplus -s sys/oracle as sysdba << __EOF__
set timing on
set echo on
-- SELECT $1 from dual;
CREATE PLUGGABLE DATABASE pdb_$1
  ADMIN USER  pdb_$1 IDENTIFIED BY oracle
  ROLES = (dba)
  FILE_NAME_CONVERT = ('/u01/app/oracle/oradata/cdb1/pdbseed/',
                       '/home/oracle/pdbtest/$1/');
   drop pluggable database pdb_$1 including datafiles;
exit;
__EOF__
[oracle@localhost pdbtest]$ 

The output below.

[oracle@localhost pdbtest]$ ./a.sh
starting PDBS at  Thu Sep 12 12:42:06 UTC 2013
Welcome 1 times
Welcome 2 times
Welcome 3 times
Welcome 4 times
Welcome 5 times

Pluggable database created.

Elapsed: 00:00:29.82

Pluggable database created.

Elapsed: 00:00:30.04

Pluggable database dropped.

Elapsed: 00:00:00.45

Pluggable database created.

Elapsed: 00:00:30.29

Pluggable database dropped.

Elapsed: 00:00:00.37

Pluggable database dropped.

Elapsed: 00:00:00.30

Pluggable database created.

Elapsed: 00:00:30.59

Pluggable database created.

Elapsed: 00:00:30.67

Pluggable database dropped.

Elapsed: 00:00:00.18

Pluggable database dropped.

Elapsed: 00:00:00.16
Ending  PDBS at  Thu Sep 12 12:42:38 UTC 2013