Any Oracle Database Server consists of minimum one database Instance and a Database.
Memory and the process structures are handled by the instance. Database is a collection of physical files called datafiles, control files, redo log files, password files and other system files for the database operations.
Database can be a Non Container or Multi-tenant Container database.
We can have a single instance database or multiple instances that operate as a single database using Oracle Real Application Clusters (RAC). In RAC, multiple instances can be installed on separate servers and all these share a common database files. RAC provides clustering to provide High Availability, Scalability and better performance.
Instance consists of memory structures and background processes. Memory structures include System Global Area (SGA) and Program Global Area (PGA).
There are mandatory and optional background processes which operate on the database files and depend on memory structures to do their tasks.
Server Process handles the connections to the database for the clients. It performs parsing and executing SQL statements, extracting and returning the results to the users or client program. Server Process is also called foreground process.
Listener is the process that receives the client/application requests, creates connection to the database instance and forwards the client connection to the server process
No comments:
Post a Comment