I have my Sitecore multisite up and running.(Version 8.2).The values and data are populated on both Mongodb and SQL databases.But May I know what is the use of Analytics Database stored on the SQL server, and how the data is being captured and stored on the sql database.Is there any links/documents available ,to explain the same.
The Analytics DB is used as a reporting database for xDB. MongoDB is the collection database and periodically this is aggregated and stored in the Analytics db (also called the reporting db).
If you are disabling xDB and Tracking, then there is no need for the Analytics DB.