The CA WA job is looking for same environment that a user profile exports. You can reproduce this on your UNIX by running the command as a user that does not have Oracle related profile setup.
[root@oracle]# sqlplus / as sysdba
Error 6 initializing SQL*Plus
Message file sp1<lang>.msb not found
SP2-0750: You may need to set ORACLE_HOME to your Oracle software directory
Now, with profile setup
[root@WAR53BWA bin]# export ORACLE_HOME=/opt/oracle/product/10.2.0/db_1
[root@WAR53BWA bin]# sqlplus / as sysdba
SQL*Plus: Release 10.2.0.1.0 - Production on Wed Aug 1 14:11:01 2012
Copyright (c) 1982, 2005, Oracle. All rights reserved.
Enter user-name:
[color=#ff021c]Note: [color]This is an example. Do not run sqlplus as root without consulting your DBA.
Set the user in the CA WA job that can run sqlplus correctly (usually not root). You may also want to set this in the agentparm.txt:
oscomponent.defaultshell.force=trueThe agent will then use the default shell to run UNIX scripts and to source the user's profile.