Summary Database Management Systems DBMSs is the basic and main component of computer world and has came up with many system design techniques to resolve the scalability security and reliability issues Relational database management systems RDBMSs is one of the commonly used database systems The architecture of Database system includes different main components in which initially the client calls the API which forms a connection with the Client Communications Manager of a DBMS thereby forming two tier Client server system or three tier system with middleware server in addition or four tier server having application server in addition Thus DBMS responds to the SQL commands from the clients and send the data with a proper controlling system taking care of results errors security etc After receiving the command from the client it is assigned to the thread of computation by the Process Manager which also takes care of admission control i e when to process the queries dispatch and scheduling Then query is processed by invoking the Relational Query Processor which handles the query authorizations query rewrite and optimizations then compiles the query into internal query plan which is maintained by the plan executor consisting of different relational algorithm implementations like selection joins sorting projection aggregation requesting data records from lower layers of database system by calling Transactional Storage Manager which controls the access and calls to the data using buffer manager access methods log manager and lock manager
