Ora-01034 for users other than oracle

Question

Hello.
I am having an issue when trying to connect through SQLPLUS with users that aren,t oracle user. Database instance is mounted, opened and working fine, listener also is up and running. I,m able to login without any issues with oracle user as follow:
[oracle@LX-TSC2 admin]$ sqlplus metro_ctl/metro_ctl
SQL*Plus: Release 10.2.0.4.0 - Production on Sat Oct 26 08:30:44 2013
Copyright (c) 1982, 2007, Oracle.  All Rights Reserved.
Connected to:
Oracle Database 10g Release 10.2.0.4.0 - Production
SQL>
But if I try with another linux user, I get errors:
[metro_ctl@LX-TSC2 ~]$ sqlplus metro_ctl/metro_ctl
SQL*Plus: Release 10.2.0.4.0 - Production on Sat Oct 26 08:31:58 2013
Copyright (c) 1982, 2007, Oracle.  All Rights Reserved.
ERROR:
ORA-01034: ORACLE not available
ORA-27101: shared memory realm does not exist
Linux Error: 2: No such file or directory
ORACLE_SID, ORACLE_HOME, PATH are already defined as enviroment variable for user metro_ctl:
[metro_ctl@LX-TSC2 ~]$ echo $ORACLE_SID
TSC
[metro_ctl@LX-TSC2 ~]$ echo $ORACLE_HOME
/oracle/product/10.2.0/db_1
[metro_ctl@LX-TSC2 ~]$ echo $PATH
/home/metro_ctl/fuentes/java/classes:/home/metro_ctl/fuentes/java/lib/classes12.zip:/home/metro_ctl/fuentes/java/bcprov-jdk14-128.jar:/usr/java/j2sdk1.4.1_01:/usr/kerberos/bin:/usr/local/bin:/bin:/usr/bin:/usr/X11R6/bin:/home/metro_ctl/bin:.:/oracle/product/10.2.0/db_1:/oracle/product/10.2.0/db_1/bin:/oracle/product/10.2.0/db_1/lib:/home/metro_ctl/pipe:/home/metro_ctl/bin
I am able to login without problems with user metro_ctl if I specified that SID at the sqlplus :
[metro_ctl@LX-TSC2 ~]$ sqlplus metro_ctl/metro_ctl@TSC
SQL*Plus: Release 10.2.0.4.0 - Production on Sat Oct 26 08:34:42 2013
Copyright (c) 1982, 2007, Oracle.  All Rights Reserved.
Connected to:
Oracle Database 10g Release 10.2.0.4.0 - Production
SQL>
But I don,t want to specified the SID since it is already specified in the enviroment variable ORACLE_SID, I want to login just using 'sqlplus metro_ctl/xxx'
In case needed, I paste the following:
[oracle@LX-TSC2 admin]$  ps -ef|grep pmo
oracle   24463     1  0 06:32 ?        00:00:00 ora_pmon_TSC
[oracle@LX-TSC2 admin]$ cat tnsnames.ora
# tnsnames.ora Network Configuration File: /oracle/product/10.2.0/db_1/network/admin/tnsnames.ora
# Generated by Oracle configuration tools.
TSC =
  (DESCRIPTION =
    (ADDRESS = (PROTOCOL = TCP)(HOST = LX-TSC2)(PORT = 1521))
    (CONNECT_DATA =
      (SERVER = DEDICATED)
      (SERVICE_NAME = TSC)
[oracle@LX-TSC2 admin]$ cat listener.ora
SID_LIST_LISTENER =
  (SID_LIST =
    (SID_DESC =
      (SID_NAME = TSC)
      (ORACLE_HOME = /oracle/product/10.2.0/db_1)
      (PROGRAM = extproc)
LISTENER =
  (DESCRIPTION_LIST =
    (DESCRIPTION =
      (ADDRESS = (PROTOCOL = TCP)(HOST = LX-TSC2)(PORT = 1521))
      (ADDRESS = (PROTOCOL = IPC)(KEY = EXTPROC0))
[metro_ctl@LX-TSC2 ~]$ tnsping TSC
TNS Ping Utility for Linux: Version 10.2.0.4.0 - Production on 26-OCT-2013 08:37:56
Copyright (c) 1997,  2007, Oracle.  All rights reserved.
Used parameter files:
Used TNSNAMES adapter to resolve the alias
Attempting to contact (DESCRIPTION = (ADDRESS = (PROTOCOL = TCP)(HOST = LX-TSC2)(PORT = 1521)) (CONNECT_DATA = (SERVER = DEDICATED) (SERVICE_NAME = TSC)))
OK (0 msec)
Any help will be appreciate.

Answer 1

Hello.
I finally did solved my problem   . I want to thank to all the people who tried to help me with my issue. I am now able to use sqlplus without using SID at the end:
metro_ctl@LX-TSC2$ sqlplus metro_ctl/metro_ctl
SQL*Plus: Release 10.2.0.4.0 - Production on Sat Oct 26 13:41:51 2013
Copyright (c) 1982, 2007, Oracle.  All Rights Reserved.
Connected to:
Oracle Database 10g Release 10.2.0.4.0 - Production
SQL> select * from cat where rownum < 7;
TABLE_NAME                     TABLE_TYPE
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
I solved it doing the following steps:
1)Log on as root and change permission.
bash-3.00$ su Password:
# umask 022
# cd $ORACLE_HOME
# chmod 755 *
# cd $ORACLE_BASE/admin/$ORACLE_SID
# chmod 755 *
# cd $ORACLE_HOME/bin
# chmod 6751 oracle
# exit