The limitation if file systems that can be overcome by a relational DBMS are:
Data Redundancy: redundancy means repetition of same data in different tables. Redundancy leads to excess data storage and may cause data inconsistency.
Data Inconsistency: When same data is managed differently in different places leads to data inconsistency. Data inconsistency creates unreliable information, because it will be difficult to determine which version of information is correct.
Data Isolation: In file system because data mapping (link) is not supported, so all the files (table with records) are created and kept in isolation. This is called data isolation and it becomes very difficult to keep database in same state after the execution of a transaction.
Data Dependence: data are stored in a specific format or structure in a file. If the structure or format is changed, all the existing application programs accessing that file also need to change. Otherwise, the programs may not work correctly.
Controlled Data Sharing: it is very difficult to provide access control of data at different level for different user in a file system.