From Oracle FAQ
CMAN.ORA is a text file containing settings for the SQL*Net Connection Manager (CM).
Sample CMAN.ORA file
CMAN = (ADDRESS=(PROTOCOL=tcp)(HOST=126.96.36.199)(PORT=1610)) CMAN_ADMIN = (ADDRESS=(PROTOCOL=tcp)(HOST=188.8.131.52)(PORT=1650)) CMAN_RULES = (RULE_LIST = (RULE = (SRC=141.145.*.*) # Wildcard is "x" (DST=141.145.*.*) (SRV=orcl) (ACT=ACC) )) CMAN_PROFILE = (PARAMETER_LIST= (MAXIMUM_RELAYS=8) # Default is normally too small (LOG_LEVEL=1) (TRACING=NO) (SHOW_TNS_INFO=YES) (RELAY_STATISTICS=NO) )
Route a connection through the Connection Manager
Code a TNSNAMES.ORA entry with two addresses. The first address specifies the address Connection Manager is listening on (coded in CMAN.ORA). The second is the address the outgoing traffic must be routed to. You also need to specify SOURCE_ROUTE=YES.
cman_entry = (DESCRIPTION = (ADDRESS_LIST = (ADDRESS=(PROTOCOL=TCP)(HOST=host1.com)(PORT=1610)) (ADDRESS=(PROTOCOL=TCP)(HOST=host2.com)(PORT=1923)) ) (CONNECT_DATA = (SERVICE_NAME = orcl) ) (SOURCE_ROUTE = YES) )