I created a record type before in my application and right now I don't need anymore. I tried to delete from application but I got it this error. What is the problem?
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A "constraint violation" sounds like there might be some remaining dependencies in the database.
This record type is used to store data from web service API and we do not have any table in our database.
Yes, you do. A record type cannot store any data on its own.
The table exist to another database application, not in ours. Could it be this problem?
also I removed the source from record type.
Try removing a couple of precedents from the record and then delete it. If it is being used in any relationships in other records, delete those relationships and try again.