In this codebase only one module has been called that is Oraperl.pm. this module is being used for Unix OS .For example for db connectivity from unix,the code is

$n = &ora_login($db, $ui, $pwd);
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for db connectivity from windows NT,the code is

($n, $err, $errtext) = ::ODBC_Connect($DSN);
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From this code, i understood ora_login is from Oraperl.pm but cannot understand where ODBC_Connect is coming from.