This post is not a question. I wanted to share that I was having trouble connecting with TNS alias and kept getting ORA-12504. One of the posts was very helpful in identifying the difference between SERVICE_NAME and SID. How are these different and how to configure them in TNSNAMES.ora and LISTENER.ora files. I fixed all that and still kept getting the same error.
A simple post on dba-oracle.com solved the problem. It was making sure to align the close parenthesis for the ADDRESS tag.
ORA-12504 TNS Listener Not Given SID
That fixed it! Hope it is useful to you too!!