Unable to connect to SYS

Question

Hi all,
i am suddenly not able to connect to SYS ... I am being able to connect SYSTEM though and am also being able to do this
SQL> conn system
Enter password: ******
Connected.
SQL> alter user sys identified by sys;
User altered.
SQL> conn sys/sys as sysdba;
ERROR:
ORA-01031: insufficient privileges
Warning: You are no longer connected to ORACLE.
SQL>
Please advice

Answer 1

ok now i am getting this..
SQL> conn sys/sys as sysdba
ERROR:
ORA-12560: TNS:protocol adapter error
SQL> conn scott/tiger
ERROR:
ORA-12560: TNS:protocol adapter error
after
D:\oracle\product\10.1.0\db_1\BIN>orapwd file=orapworcl password=sys entries=20
force=y
D:\oracle\product\10.1.0\db_1\BIN>sqlplusw /nolog
my tnsnames.ora looks like this..
orcl =
(DESCRIPTION =
(ADDRESS = (PROTOCOL = TCP)(HOST = 172.28.51.70)(PORT = 1521))
(CONNECT_DATA =
(SERVER = DEDICATED)
(SERVICE_NAME = orcl)
I have also commented the sqlnet.ora #SQLNET.AUTHENTICATION_SERVICES= (NTS)
and i've got a sqlnet.log file in BIN that has following error message
Fatal NI connect error 12560, connecting to:
(DESCRIPTION=(ADDRESS=(PROTOCOL=BEQ)(PROGRAM=oracle)(ARGV0=oracleTEST)(ARGS='(DESCRIPTION=(LOCAL=YES)(ADDRESS=(PROTOCOL=beq)))'))(CONNECT_DATA=(SID=orcl)(CID=(PROGRAM=d:\oracle\product\10.1.0\db_1\bin\sqlplus.exe)(HOST=PC081)(USER=xyz))))
Please advice..