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Introduction

MongoDB is a collection-oriented, schema-free document database.

By collection-oriented, we mean that data is grouped into sets that are called 'collections'. Each collection has a unique name in the database, and can contain an unlimited number of documents. Collections are analogous to tables in a RDBMS, except that they don't have any defined schema.

By schema-free, we mean that the database doesn't need to know anything about the structure of the documents that you store in a collection. In fact, you can store documents with different structure in the same collection if you so choose.

By document, we mean that we store data that is a structured collection of key-value pairs, where keys are strings, and values are any of a rich set of data types, including arrays and documents. We call this data format "BSON" for "Binary Serialized dOcument Notation."

MongoDB Operational Overview

MongoDB is a server process that runs on Linux, Windows and OS X. It can be run both as a 32 or 64-bit application. We recommend running in 64-bit mode, since Mongo is limited to a total data size of about 2GB for all databases in 32-bit mode.

The MongoDB process listens on port 27017 by default (note that this can be set at start time - please see Command Line Parameters for more information.

Clients connect to the MongoDB process, optionally authenticate themselves if security is turned on, and perform a sequence of actions, such as inserts, queries and updates.

MongoDB stores its data in files (default location is /data/db/), and uses memory mapped files for data management for efficiency.

MongoDB can also be configured for automatic data replication , as well as automatic fail-over .

For more information on MongoDB administration, please see Mongo Administration Guide.

MongoDB Functionality

As a developer, MongoDB drivers offer a rich range of operations:

• Queries: Search for documents based on either query objects or SQL-like "where predicates". Queries can be sorted, have limited return sizes, can skip parts of the return document set, and can also return partial documents.
• Inserts and Updates : Insert new documents, update existing documents.
• Index Management : Create indexes on one or more keys in a document, including substructure, deleted indexes, etc
• General commands : Any MongoDB operation can be managed via DB Commands over the regular socket.