Currently I'm setup an oracle 11g on solaris and arcsde10 on linux machine.
Both setup are successful. But i having difficulty to connect from arccatalog.
The error return "FAILED TO CONNECT TO DATABASE.OPERATION FAILED".
I can start the arcsde using command "sdemon -o start -i esri_sde2 -p SDE
The esri_sde2 using port 5151 stated on dbinit.sde and services.sde also in etc/services file
Also I can connect from arcsde10 machine using oracle11g client to oracle11g db on solaris server.
The error on sde_esri_sde2.log stated "
[Wed Jan 7 15:28:23 2015]  [GIOMGR] Error (-1):Couldn't Start Server Task.
/arcsde/sdeexe100/bin/gsrvr: error while loading shared libraries: libclntsh.so.
11.1: cannot open shared object file: No such file or directory "
I set the LD_LIBRARY_PATH to $SDEHOME/lib and $ORACLE_HOME/lib.
Is there any setting i miss out? Please help me