SQL*Net FAQ

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Oracle SQL*Net (Net8) FAQ:

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What is SQL*Net/ Net8?

Net8 (called SQL*Net prior to Oracle8) is Oracle's client/server middleware product that offers transparent connection from client tools to the database, or from one database to another.

Net8 enables services and their applications to reside on different computers and communicate as peer applications. The main function of Net8 is to establish network sessions and transfer data between a client machine and a server or between two servers. Net8 is located on each machine in the network. Once a network session is established, Net8 acts as a data courier for the client and the server.

Essentially, SQL*Net provides the software layer between Oracle and the networking software, providing seamless communication between an Oracle client machine (running, for example, SQL*Plus) and the database server or from one database server to another. SQL*Net/ Net8 works across multiple network protocols and operating systems.

TNS or Transparent Network Substrate is Oracle's networking architecture. TNS provides a uniform application interface to enable network applications to access the underlying network protocols transparently.

The TNS architecture consists of three software components:

  • TNS-based applications (like SQL*Plus or TOAD)
  • Oracle Protocol Adapters (OPA)
  • Networking software like TCP/IP
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What is the difference between SQL*Net V1, V2 and NET8?

  SQL*Net V1 SQL*Net V2 Net8 and above
Default port 1525/tcp 1521/tcp 1521/tcp
Start command tcpctl start lsnrctl start lsnrctl start
Stop command tcpctl stop lsnrctl stop lsnrctl stop
Connect string protocol:host:sid eg. T:SRV1:DB1 Specified in TNSNAMES.ORA Specified in TNSNAMES.ORA
Config files /etc/oratab tnsnames.ora, sqlnet.ora & listener.ora tnsnames.ora, sqlnet.ora & listener.ora
Env variable LOCAL= TWO_TASK= TWO_TASK=
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Where are the SQL*Net configuration files located?

The SQL*Net configuration files (like SQLNET.ORA and TNSNAMES.ORA) can be found in one of the following locations (SQL*Net searches for it in this order):

  • Directory pointed to by the TNS_ADMIN parameter ($TNS_ADMIN on Unix)
  • /etc (Unix only)
  • /var/opt/oracle (Unix only)
  • $ORACLE_HOME/network/admin (or sometimes net8/admin directory)
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