Oracle SQL NET transparent network Oracle Tips by Burleson Consulting

The Data Warehouse Development Life Cycle

The Internals Of Oracle's SQL*Net

In version 2.0, Oracle has added several important enhancements to SQL*Net. Aside from the badly needed bug fixes, SQL*Net now allows multiple community access. A community is a group of computers that shares a common protocol (such as TCP/IP to LU6.2). In addition, the Oracle database engine now defines a multithreaded server (MTS) for servicing incoming data requests. In the MTS, all communications to the database is handled through a single dispatcher. In SQL*Net version 1.0, a separate process is spawned for each connection. These connections are easily viewed by using the Unix ps command.

When upgrading from SQL*Net 1.0 to SQL*Net 2.0, you should be aware of subtle differences between how the two versions handle communications (see Figure 9.12). SQL*Net version 1.0 uses an orasrv component on the destination database to listen for incoming requests, while SQL*Net 2.0 uses a process called tnslsnr (TNS listener). In addition, SQL*Net 1.0 cannot use the multithreaded server.

Figure 9.12 The two versions of SQL*Net.

When a connection is made to SQL*Net, it passes the request to its underlying layer--the transparent network substrate (TNS)--where the request is transmitted to the appropriate server. At the server, SQL*Net receives the request from TNS and passes the SQL to the database. Transparent network substrate is a fancy phrase meaning a single, common interface to all protocols that allows you to connect to databases in physically separate networks. At the lowest level, TNS communicates to other databases with message-level send and receive commands.

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This is an excerpt from "High Performance Data Warehousing", copyright 1997.

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