On database server: Add (SDU = 32768) to SID_DESC section for the instance under SID_LIST_LISTENER in listener.ora SID_LIST_edwt = (SID_LIST = (SID_DESC = (SDU = 32768) (GLOBAL_DBNAME= edwt) (ORACLE_HOME= /app/oracle/product/edwt/8.1.6.3) (SID_NAME = edwt) ) Add this to sqlnet.ora (temporarily, for verification purpose only): trace_level_server=16 trace_directory_server=/tmp trace_file_server=server.trc On the client: Add (SDU = 32768) to DESCRIPTION section in tnsnames.ora: edwt = (DESCRIPTION = (SDU = 32768) (ADDRESS = (PROTOCOL = tcp) (Host = janus.sgld.uc.com) (Port = 1526) ) (CONNECT_DATA = (SID = edwt) ) ) Add this sqlnet.ora (temporarily, for verification purpose only): trace_level_client=16 trace_directory_client=/tmp trace_file_client=client.trc trace_unique_client = true On server, lsnrctl reload To verify, Run a query in sqlplus. Check the trace files on server and client. Also check by ps -ef | grep LOCAL or grep SDU on the server truss -t pread -p (on Linux use strace) should show 32768 bytes are read at a time when the file descriptor (first arg in pread()) is the SQL*Net socket.