what is the difference between Security Context Ledger and Data Access set created for Ledger-?

Summary:

Difference of functionality wise between Security Context setup at Ledger level and Data Access set created for full Ledger Access.

Content (please ensure you mask any confidential information):

In order to give a General Ledger Data access to user Primarily we use Data Access Set. This data access set is defined at fully Ledger level. It is usually sufficient to give access to Ledger Data. There is an option to setup Security Context at Ledger level as well. What is the use of this security Context at Ledger level. Does it have same functionality as data access set or something else. Also please consider scenario where there are multiple Primary ledgers are defined in same instance.