Pro*C – PCC-F-02104, Unable to connect to Oracle

If you are attempting to compile Pro*C code and get the error “PCC-F-02104, Unable to connect to Oracle”, perform the following steps:

Instead of connecting to the Oracle database as

sqlplus userid/password@somelistener.domain.com:1521/MYPRODDB

and then attempting to compile, edit your tnsnames.ora to add the below entry (change appropriately to reflect your database SID or service, listener, port etc.)

MY_DB =
  (DESCRIPTION =
    (ADDRESS = (PROTOCOL = TCP)(HOST = SOMELISTENER.DOMAIN.COM)(PORT = 1521))
    (CONNECT_DATA =
      (SERVER = DEDICATED)
      (SID = MYPRODDB)
    )
  )

Export this entry as follows

export TWO_TASK=MY_DB

And now connect as

sqlplus userid/password

i.e. without specifying the usual connect string.

In case you are wondering about the name “TWO_TASK”, Tom Kyte explains it best:
“because in days gone by – the 1980’s – two tasks (having two tasks working together) just made ‘sense’”.