how much time does a synonym take to update the fields that are changed in the parent table? is it some configurable parameter?

Hi,

Well, negligible or highly insignificant. No it's not configurable parameter at all. While a synonym is active on a table, and table is called or referenced by synonym-name, database engine has to access an additional base table - syssynonyms for relations information on base and other name.

Regards,
Shriyan