Session:  A Session is a set of instructions that tells the Informatica Server how and when to move data from Source to Target. After creating the session, we can use either the server manager or the command line program pmcmd to start or stop the session.

Batches: It provides a way to group sessions for either serial or parallel execution by the Informatica Server. There are two types of batches:

• Sequential – Run Session one after the other.
• Concurrent – Run Session at the same time.

1. What is the primary purpose of using surrogate key?
2. Will those be used in fact tables? If not then what is the purpose in using it?

Answer:

Surrogate key is used for indexing purpose  i.e. as a primary key for a table.

Reason of using Surrogate Key over Primary Key:
Primary Key may take more or less memory i.e. it may contain characters but Surrogate Key contains only number.  So comparison of numbers is easy when comparing with characters. 

Yes, Surrogate Key will be used in fact tables to establish a relationship between dimensions.  Surrogate keys are implemented by using the Sequence generator.