This error is very typical especially in version 11g. Is a level problem sockets. From the side of the database we can not do anything because usually it come induced because of no response from the client / service where it is called. In most of the cases is caused by calls to UTL_HTTP and UTL_TCP. Consider the following example.
select utl_http.request(‘http://sql1.wordpress.coN’) from dual
If we call a web page that does not exist, and we see from another session the event of waiting for the first session we will see this is the “TCP Socket (KGAS)”. On the other way, the first session, where we execute the select statement, will return the following error;
REM The language is Spanish, but the error code are the same select utl_http.request('http://sql1.wordpress.coN') from dual * ERROR en línea 1: ORA-29273: fallo de la solicitud HTTP ORA-06512: en "SYS.UTL_HTTP", línea 1722 ORA-12535: TNS:timeout de la operación ORA-06512: en línea 1
HTH – Antonio NAVARRO.