Tracing the Oracle client … a first file shows that all my tnsnames.ora is loaded in the right way, the second file is :
(1976) [22-JUN-2015 17:11:10:172] — TRACE CONFIGURATION INFORMATION FOLLOWS —
(1976) [22-JUN-2015 17:11:10:173] New trace stream is c:\app\oracle\product\10.2.0\NETWORK\log\cli_1976_1.trc
(1976) [22-JUN-2015 17:11:10:173] New trace level is 16
(1976) [22-JUN-2015 17:11:10:173] — TRACE CONFIGURATION INFORMATION ENDS —
(1976) [22-JUN-2015 17:11:10:173] — PARAMETER SOURCE INFORMATION FOLLOWS —
(1976) [22-JUN-2015 17:11:10:173] Attempted load of system pfile source c:\app\oracle\product\10.2.0\NETWORK\ADMIN\sqlnet.ora
(1976) [22-JUN-2015 17:11:10:173] Parameter source loaded successfully
(1976) [22-JUN-2015 17:11:10:173]
(1976) [22-JUN-2015 17:11:10:173] Attempted load of local pfile source C:\Program Files (x86)\Dell\Toad for Oracle 2015 Suite\Toad for Oracle 12.7\sqlnet.ora
(1976) [22-JUN-2015 17:11:10:173] Parameter source was not loaded
(1976) [22-JUN-2015 17:11:10:173]
(1976) [22-JUN-2015 17:11:10:173] -> PARAMETER TABLE LOAD RESULTS FOLLOW <-
(1976) [22-JUN-2015 17:11:10:173] Successful parameter table load
(1976) [22-JUN-2015 17:11:10:173] -> PARAMETER TABLE HAS THE FOLLOWING CONTENTS <-
(1976) [22-JUN-2015 17:11:10:173] trace_directory_client = c:\app\oracle\product\10.2.0\NETWORK\log
(1976) [22-JUN-2015 17:11:10:173] NAMES.DIRECTORY_PATH = (TNSNAMES)
(1976) [22-JUN-2015 17:11:10:173] trace_level_client = 16
(1976) [22-JUN-2015 17:11:10:173] SQLNET.AUTHENTICATION_SERVICES = (none)
(1976) [22-JUN-2015 17:11:10:173] trace_unique_client = true
(1976) [22-JUN-2015 17:11:10:173] trace_file_client = cli
(1976) [22-JUN-2015 17:11:10:173] trace_timestamp_client = ON
(1976) [22-JUN-2015 17:11:10:173] — PARAMETER SOURCE INFORMATION ENDS —
(1976) [22-JUN-2015 17:11:10:173] — LOG CONFIGURATION INFORMATION FOLLOWS —
(1976) [22-JUN-2015 17:11:10:173] Log stream will be “C:\Program Files (x86)\Dell\Toad for Oracle 2015 Suite\Toad for Oracle 12.7\sqlnet.log”
(1976) [22-JUN-2015 17:11:10:173] Log stream validation not requested
(1976) [22-JUN-2015 17:11:10:173] — LOG CONFIGURATION INFORMATION ENDS —
(1976) [22-JUN-2015 17:11:10:173] nlstdipi: entry
(1976) [22-JUN-2015 17:11:10:173] nlstdipi: exit
(1976) [22-JUN-2015 17:11:10:173] nigini: entry
(1976) [22-JUN-2015 17:11:10:174] nigini: Count in the NL global area is now 1
(1976) [22-JUN-2015 17:11:10:174] nigini: Count in NI global area now: 1
(1976) [22-JUN-2015 17:11:10:174] nrigbi: entry
(1976) [22-JUN-2015 17:11:10:174] nrigbni: entry
(1976) [22-JUN-2015 17:11:10:174] nrigbni: Unable to get data from navigation file tnsnav.ora
(1976) [22-JUN-2015 17:11:10:174] nrigbni: exit
(1976) [22-JUN-2015 17:11:10:174] nrigbi: exit
(1976) [22-JUN-2015 17:11:10:174] nigini: exit
(1976) [22-JUN-2015 17:11:10:174] niqname: Hst is already an NVstring.
(1976) [22-JUN-2015 17:11:10:174] niqname: Inserting CID.
(1976) [22-JUN-2015 17:11:10:174] nigtrm: Count in the NI global area is now 0
(1976) [22-JUN-2015 17:11:10:174] nrigbd: entry
(1976) [22-JUN-2015 17:11:10:174] nrigbd: exit
(1976) [22-JUN-2015 17:11:10:174] nigtrm: Count in the NL global area is now 0
(1976) [22-JUN-2015 17:11:10:174] nlse_term_audit: entry
(1976) [22-JUN-2015 17:11:10:174] nlse_term_audit: exit
please note :
(1976) [22-JUN-2015 17:11:10:174] nrigbni: Unable to get data from navigation file tnsnav.ora
very odd behaviour !