1. Normal mode:

OraCmd > connect username/password@host:port:SID(or Service Name);

example:

or:

OraCmd userid=username/password@host:port:SID(or Service Name)

example:

If you want to hide password, use:

OraCmd > connect username@host:port:SID(or Service Name);

example:

or:

OraCmd userid=username@host:port:SID(or Service Name)

example:

2. SysDBA mode:

OraCmd > connect username/password@host:port:SID(or Service Name) as sysdba;

or:

OraCmd userid=username/password@host:port:SID(or Service Name) mode=sysdba

To hide password, use:

OraCmd > connect username@host:port:SID(or Service Name) as sysdba;

or:

OraCmd userid=username@host:port:SID(or Service Name) mode=sysdba

3. SysOper mode:

OraCmd > connect username/password@host:port:SID(or Service Name) as sysoper;

or:

OraCmd userid=username/password@host:port:SID(or Service Name) mode=sysoper

To hide password, use:

OraCmd > connect username@host:port:SID(or Service Name) as sysoper;

or:

OraCmd userid=username@host:port:SID(or Service Name) mode=sysoper

Disconnect from Oracle:

OraCmd > disconnect;