After we update the Base Calendar like making few Working days as non-Working or vice versa. What jobs need to be run after these changes ?
If jobs are not run will this effect resources availability reports ?
Time slicing.
If you have a lot of resources and a lot of "wide" time slice settings, this will take a while ; all availability slices for resources that use the base calendar will be completely rebuilt. (so "yes" if you don't run the job any availability reports that use the slices will be out of date)
You said "This will take a while" it mean "time slicing" Job ?
Yes the time slicing job will be doing a lot of work ; it will remove and completely rebuild the availability slices for any resource that uses the base calendar. Depending upon how many resources you have in the system (and how your slices are configured) this is potentially a long running job.