Q. Rest API Invalid Session Id Error In salesforce
Ans:
When you sign on via the login() call, a new client session begins and a corresponding unique session ID is generated. Sessions expire automatically after a predetermined length of inactivity, which can be configured in Salesforce from Setup by clicking Security Controls. The default is 120 minutes (two hours). If you make an API call, the inactivity timer is reset to zero.
When your session expires, the exception code INVALID_SESSION_ID is returned. If this happens, you must invoke the login() call again.
