Obtaining TNS entries from PL/SQL

Question

I read somewhere that one can get TNS entry definitions via PL/SQL.
We currently develope/maintain a project on Oracle 9.2.0 which interconnects to at least 3 other projects running oracle instances. The problem here is that we have multiple development, testing, BC/DR and production instances to keep track of. and we need to know the dblink definitions that each of our instances connects to. Obviously we can get the tnsname of the dblink from "select * from all_db_links", but using tnsping returns the definition of that tnsentry from our local client (ugh). we need to be able to write a small stored function to query the tns definition from the server itself to ensure we have the correct definition relayed.
Is this possible?

Answer 1

Not really... not in a nice clean and robust way.
PL/SQL itself does not have a command or standard package to enumurate the local list of TNS aliases in the tnames.ora file. And using UTL_FILE and parsing the tnsnames.ora file is not trivial.
Question though is why use the tnsnames.ora file on the server in the first place? If you db connectivity and management is driven at application level, then dealing with the actual db connection data externally (in a flat file) is a problem. So don't. Deal with it inside Oracle itself.
You can define a db link in Oracle using the actual connection string itself (which is what the TNS alias refers to).
E.g.
create database link orcl_test connect to scott identified by tiger using
'(DESCRIPTION=(ADDRESS_LIST=(ADDRESS=(PROTOCOL=TCP)(HOST=10.0.0.1)(PORT=1527))) (CONNECT_DATA=(SID=orcl)(SERVER=shared)))';
At application level you can control the type of connection ito service name,/SID, TAF, shared/dedicated and so on.
Obviously there are pro's and con's both ways - using a tnsnames.ora file versus using the connection string directly. But in certain cases the pro's outweigh the con's.