@MonikaS9010 To connect pega with external DB there you need to follow below steps :   

1. In the header of Dev Studio, click Create>SysAdmin>Database.
2. In the Create database tab, enter a short description, and in the Database field, enter a name for the external database.

   The database name is case-sensitive.

3. Click Create and open.
4. Optional: To indicate the system of record, in the Integration system field, press the Down arrow key, and then select the name of the integration system that you want to associate with this database.

   The value that you select is for informational purposes only, and does not affect the behavior of the database instance. You can use this value to organize rules for integration connectors, data types, and sources for data pages.

5. In the How to connect list, click Use JDBC URL listed below.
6. In the JDBC URL field, enter the JDBC URL.

   The format of the JDBC URL depends on the database platform. Precise syntax requirements and parameters vary depending on the server platform, database version, and JDBC client. Consult your database administrator for details. Link : External DB Error while Connection : Error might occur Thanks