Will commit inside a loop reduce the performance of query? Also I have a doubt about using PL/SQL. Will using PL/SQL has any effect on performance?

Generally to say I would suggest not to use commit inside loop and also I would suggest using SQL wherever possible by reducing PL/SQL. But when needed it is used as per the requirements.

When I was going through this discussion I happened to come across some concept or term called Parallel Query. But I could not get any information or description about this. Somebody highlight whether it is related to this discussion. In other words can this Parallel query can be used to improve performance. If so what does the concept actually mean?

Definitely Parallel Query will improve Performance but the commit statement problem is nothing to do with Parallel Query.

Oracle implemented the concept of Parallelism using Oracle Parallel Query(OPQ) or Parellel Execution.
When Oracle has to perform a large, full-table scan, OPQ can make a dramatic difference in the response time
Parallelism is the idea of breaking down a task so that, instead of one process doing all of the work in a query, many processes do part of the work at the same time.
The performance will improve drastically by this method.

When SQL statement is executed in Oracle, multiple processes work together simultaneously to run a single SQL statement.
By dividing the job necessary to run a statement among multiple processes, Oracle can run the statement more quickly than a single process.
This is called Parallel Execution or Parallel Processing.

*** Innila ***