I just wanted know the entry limits of Event Journal component and Alarm Status Table component. Is there any limit to the entries to these components?
There are no limits in standard Ignition. Just whatever your database can handle.
In more detail:
The components are just views to the backing data that's controlled by the gateway. The individual components (in Vision or Perspective) don't have any explicit builtin limits either, but are going to be limited by communication with the gateway and device limitations wherever you're actually viewing them. I wouldn't expect either component to handle viewing more than low tens of thousands of events, at most.
However, the actual data and execution engine powered by the gateway will basically scale as far as your hardware for the gateway and your DB can go, as Phil mentioned.