i am new beginner.i don't know the difference between sys account and system account,and when i use sqlplus,i can't log on as sys account,but i can log on as system account. i am so obsessed with it.please help me!!!i will really appreciate it.

Hi,
  Sys is the Internal user name and also have the interanl functions ,procedures and Tables.These database objects are used for tuning and monitoring the databases.
  This user have rights mount and dismount and all rights.This user anutomatically loaded without giving the Service name.

 But system is a default user .

Both of them is the DBA rights. Then only you login the System not in sys.
Thanks.

Regards
Adalarasu.S
xyka Software Ltd.,
Bangalore.

Adalarasu.S, thank you!!!!

if you want to log on as sys account type this at sql prompt
connect sys/password as sysdba
then you will be able to log into sys account, although the sys and system account look quite similar, there are various differnces in them as some of them are mentioned by arasu, usually the system account is dropped and some other account is created for dba, while sys account cannot be dropped and is mostly used to for administration purposes...

Regards
M