Oracle7 Administrator's Reference for UNIX
Overview of SQL*Net Version 2 Products
SQL*Net version 2 allows information to be moved and shared among disparate hardware, operating systems, databases, communication protocols and applications. Multi-user capabilities allow SQL*Net version 2 to distribute data on servers using a variety of protocols.
Oracle Protocol Adapters
For a SQL*Net client running an industry-standard protocol, an Oracle protocol adapter interfaces between the application program interface (API) of an underlying protocol and the corresponding interface of SQL*Net, as shown in Figure 9 - 1:
Figure 9 - 1. SQL*Net, Adapters, and Protocols
Different vendors supply variations of the same protocol and a protocol will vary across platforms. Figure 9 - 2 shows the Oracle protocol adapter implementations for different versions of three vendor-supplied TCP/IP protocols.
Figure 9 - 2. Adapter Implementations
A machine or node can support several protocols and protocol adapters simultaneously and belong to more than one SQL*Net communiy; one for each protocol installed.
A SQL*Net client can belong to more than one community in the following situations:
- As a client application accessing two or more networks. Installing protocols and protocol adapters allows a client to connect to applications in all communities.
- As a multi-protocol interchange connecting communities. Installing the interchange and two or more protocols and protocol adapters allows client and server applications to communicate among the communities.
Figure 9 - 3 shows the dependence of Oracle Protocol Adapters on the operating system protocol layer. The server has two Oracle instances linked to protocol adapters.
Figure 9 - 3. Adapters and the Operating System
Figure 9 - 3 shows two clients connected to the same listener process. The protocol adapters are linked to a listener, which connects to the Oracle instances. The listener:
- listens for all protocols installed on the machine
- connects the client to the proper dispatcher
- can be configured to start up a dedicated shadow process
The listener process running on the system listens for connections from other machines. After the connection is made, the listener hands off the connection to the instance. When the handoff takes place, the client and the instance communicate directly.
You can also set up multiple listeners with the following configurations:,
- one listener per protocol
- one listener per database
- two listeners for the same database
The listener.ora file controls listener configuration.
Networking Layers
Figure 9 - 4 shows the four network layers. The layers of software and hardware that make network connections possible are called the protocol stack. To install the network, you must link the layers of the protocol stack together.
Figure 9 - 4. SQL*Net Version 2 Networking Layers
The hardware layer is the machine. To communicate, server and client machines may require Ethernet or Token Ring connections.
The operating system protocol consists of operating system protocols and associated libraries, such as TCP or SPX. This layer connects and routes server hardware to the client operating system, allowing them to communicate.
SQL*Net and the protocol adapter layers perform the following functions:
- Prepare database queries and results for network communication.
- Provide character set independence. Server and clients can use EBCDIC or ASCII, and run international or 7-bit U.S. character sets. SQL*Net handles these differences transparently.
Error messages come from all the layers. As the client and server operating-system layers function as if they are connected to each other, the SQL*Net layers on a client and server have a virtual connection.
Oracle Names Server
The Oracle Names Server provides central storage of network names and addresses so network components can contact one another regardless of their physical locations on the network.
Note: All filenames listed in the Oracle Names Administrator's Guide are valid except they are in lowercase for UNIX. For example, NAMES.ORA is names.ora in UNIX.
Oracle Native Naming Adapters
Oracle native naming adapters enable network administrators to store Oracle service names in a native naming service already being used by the network. Administrators can configure each client to use Oracle Names, tnsnames.ora, or a native naming adapter to resolve Oracle service names to addresses. The Oracle Native Naming Adapters are:
- Distributed Computing Environment (DCE)
- Cell Directory Service (CDS)
- Network Information Services (NIS)
- Novell NetWare Directory Services (NDS)
The Multi-Threaded Server
Without a Multi-Threaded Server (MTS) configuration, each user process requires a dedicated server process. A new server process is created for each client requesting a connection and dedicated to the user process for the remainder of the connection.
With the MTS configuration, many user processes connect to a dispatcher process. The dispatcher routes client requests to the next available shared server process. This increases the number of supportable users, and reduces system overhead.
Use Oracle Network Manager on Windows to create the configuration files with the correct entries once you have supplied your configuration details.
Note: The BEQ Protocol Adapter, which is implemented on UNIX pipes, cannot be configured with MTS.
Sample initsid.ora Settings
Following is an example of MTS parameter settings in the initsid.ora file:
# MTS parameters in init.ora
mts_dispatchers="ipc,1" # run 1 IPC dispatcher
mts_dispatchers="tcp,1" # run 1 TCP/IP dispatcher
mts_dispatchers="spx,1" # run 1 SPX dispatcher
mts_dispatchers="decnet,1" # run 1 DECnet dispatcher
mts_max_dispatchers=10 # max no of dispatchers
mts_service=MYSID # dispatcher service name
mts_listener_address="(ADDRESS=(PROTOCOL=IPC)(KEY= MYSID))" # dispatcher service name
When you start the database, the ora_d000_sid, ora_d001_sid, ora_d002_sid, and ora_d003_sid dispatchers are started.
Client Status Monitor
The Client Status Monitor (CSM) is an application for evaluating your SQL*Net environment.
The CSM main window displays these major dialogs to access network information:
- Network Protocol Adapters
The menu bar gives access to customer support information, UNIX environment information, and a sqlnet.ora editor.