Concurrent Programs
For concurrent programs you can place in Log file / output file / fnd_log_messages table
For Log File
FND_FILE.PUT_LINE(FND_FILE.LOG,'your log statement');
For Output File
FND_FILE.PUT_LINE(FND_FILE.OUTPUT,'your output statement');
For Tracing it in a table FND_LOG_MESSAGES
fnd_log.string(log_level => fnd_log.level_statement
,module => 'custom module'
,message => 'you log message here');