Oracle NET configuration and working principle

Oracle NET configuration and working principle

Oracle NET is a software layer that supports conversion between different network protocols. Different physical machines can communicate with each other through this software layer, specifically implementing remote access to oracle.

The client provides the service name, and oracle net resolves the service name specified by the user to the corresponding server host and database instance. The TNSNAMES. ORA file on the client records the host and oracle instance corresponding to each oracle net alias;

The Oracle NET configuration files include LISTENER. ORA, TNSNAMES. ORA, SQLNET. ORA, and LDAP. ORA;

LISTENER. ORA works on the database server and monitors the connection requirements of clients that want to access the oracle database through the network;

The TNSNAMES. ORA file is on the client and records the host and oracle instance corresponding to each oracle net alias;

The database access process consists of client and server processes. The client process initiates a request, such as sqlplus. The server process reads and writes data to the database and completes various commands submitted by the user. A server process is also called a shadow process. The server process runs on the same machine as the database instance. The server LISTENER works according to the configuration file LISTENER. ORA, and serves as a bridge to bridge the client process and the shadow process.

When two processes run on the same machine, oracle uses local communication based on the inter-process (IPC). When two processes run on different machines, oracle uses oracle net to implement network communication between two processes.

The Start and Stop of oracle net is independent of the database instance. It is only responsible for sending requests from the client process to the Shadow process, and the shadow process reads and writes the database instance.

The two methods of Shared Server and multi-thread server are different from the method of using the client process of the Shadow process service.

When the client sends a request string username/passwd @ net_service_name, the oracle NET component first searches for sqlnet locally. determine the naming method of the ora file. If the name is local naming, then sqlnet. the content in ora is as follows: NAMES. DIRECTORY_PATH = (TNSNAMES ). oracle NET followed by tnsnames. ora, read the file, match net_service_name. if the net_service_name match fails, an error is returned. If the match succeeds, the system sends the correct listener according to protocol, host, and port information in connect descriptor. listener then compares the service_name in connect descritpor with the oracle services registered with it. if the comparison is successful, a connection is established. Otherwise, an error is prompted.

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