Creating DPDS database in oracle 11g.

Coming to the office this morning showing the same thing on the ubuntu desktop. so what i did just reboot it. while after that not sure what to do .. then just try to re-run the dbca when part to put the database name ("DPDS") it saying the database already created. so I just cancel it and when try to manage the database my ubuntu start to hang (i think the processing is slowing down the other processing) so i just cancel it.. and try to check by connecting to sqlplus.. then this error 'ORA-12162 "TNS:net service name is incorrectly specified" ' show up and asking for username and password when i run this command "sqlplus '/as sysdba' " and what i did, i check the /etc/oratab and i set to 'DPDS:/u01/app/oracle/product/11.1.0/db_1:Y' and i reboot it and rerun back again it clear without asking the username and password and when i try to create user then another error occur, " ORA-01034: ORACLE not available " and i exit from sqlplus and run " export $ORACLE_SID=DPDS " and run back the sqlplus command and try to create the user and give full access grant to the user. Succesfully.

My next stage would be to import dump.dmp

After successfull transfered the dump.dmp from my XP to server (using the webmin upload download services...heh heh) i create the user peran & docctrl in sqlplus + giving full access grant on DPDS. then i exit from sqlplus and run imp command then i import all from dump.dmp under user peran then docctrl.
After successful the importing, i still having problem with the ORACLE_SID and TNS_ADMIN and tnsnames.ora. Well what i did, set the
ORACLE_SID = DPDS
TNS_ADMIN=..../oradata/DPDS

in /etc/profile at below

then i set the tnsnames.ora adding the DPDS,hostname

(bla bla bla...)