Developing without Full client / tnsnames.ora

Question

I am trying to develop an OCI application using Borland C++ Builder. I want to deploy and develop using Instant Client 10G without tnsnames.ora file. I have 2 PCs - NT4 & XP.
On the NT4 PC I had installed the full Oracle Client and was using the tnsnames.ora file and things were working fine. I've since uninstalled the full client and am now getting the "ORA-12154: TNS:could not resolve the connect identifier specified" error (using Instant Client)
The XP box has never had the full client installed, does not have a tnsnames.ora file but works fine using the same code.
I've been looking through this forum and note Justin Cave's comments that you can deploy but not develop using Instant Client but this seems to work fine on my XP box. (I am an Oracle novice so I could be missing something here).
I have also checked the FAQ on connection strings and think I have got that correct (same code works on 1 PC and not the other) and don't think I've set the enviroment variables TNS_ADMIN or ORACLE_HOME on either machine.

Answer 1

Hrm, interesting. It always used to be DBQ but it seems it might have changed to SERVER at some point.
Anyway, I tried this and it worked fine for me (using 10204)
TESTFILE.DSN
================
[ODBC]
DRIVER=Oracle in OraDb10g_home1
server=(DESCRIPTION=(ADDRESS_LIST=(ADDRESS=(PROTOCOL=TCP)(HOST=gdarling-pc2)(PORT=1521)))(CONNECT_DATA=(SERVER=DEDICATED)(SERVICE_NAME=orcl)))
TEST.VBS
==========
set con = createobject("adodb.connection")
con.open "filedsn=testfile;uid=scott;pwd=tiger;"
set rs = createobject("adodb.recordset")
rs.open "select user from dual",con
msgbox rs.fields(0).value
Note also that unless you really want to create a file dsn, you could also just use a dsnless connection string and pass that directly too:
set con = createobject("adodb.connection")
con.open "driver={Oracle in OraDb10g_home1};uid=scott;pwd=tiger;server=(DESCRIPTION=(ADDRESS_LIST=(ADDRESS=(PROTOCOL=TCP)(HOST=gdarling-pc2)(PORT=1521)))(CONNECT_DATA=(SERVER=DEDICATED)(SERVICE_NAME=orcl)))"
set rs = createobject("adodb.recordset")
rs.open "select user from dual",con
msgbox rs.fields(0).value
Hope it helps,
Greg