Question: Does `dbms_output.put_line` decrease the performance in `plsql` code?

Answer: 
*Every* extra line of code decreases the performance of code. After all, it is an extra instruction to be executed, which at least consumes some CPU. So yes, dbms\_output.put\_line decreases the performance.

The real question is: does the benefit of this extra line of code outweigh the performance penalty? Only you can answer that question.

Regards,  

Rob.
Using DMBS\_OUTPUT might also be the cause of the following error:

ORA-04036: PGA memory used by the instance exceeds PGA\_AGGREGATE\_LIMIT