Hi,
A DBMS has to be persistent, that is it should be accessible when the program created the data ceases to exist or even the application that created the data restarted. A DBMS also has to provide some uniform methods independent of a specific application for accessing the information that is stored.

RDBMS is a Relational Data Base Management System Relational DBMS. This adds the additional condition that the system supports a tabular structure for the data, with enforced relationships between the tables. This excludes the databases that don't support a tabular structure or don't enforce relationships between tables.

Many DBA's think that RDBMS is a Client Server Database system but thats not the case with RDBMS.

Yes you can say DBMS does not impose any constraints or security with regard to data manipulation it is user or the programmer responsibility to ensure the ACID PROPERTY of the database whereas the rdbms is more with this regard bcz rdbms difine the integrity constraint for the purpose of holding ACID PROPERTY.

I have found many answers on many websites saying that

DBMS are for smaller organizations with small amount of data, where security of the data is not of major concern and RDBMS are designed to take care of large amounts of data and also the security of this data.

and this is completely wrong by definition of RDBMS and DBMS