Network-Configuration Files

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Network-Configuration Files

This section identifies and explains the use of network-configuration files on TCP/IP and IPX/SPX networks.

TCP/IP Connectivity Files

When you configure the database server to use the TCP/IP network protocol, you use information from the hosts and services network-configuration files to prepare the sqlhosts information.

The network administrator maintains these files. When you add a host or a software service such as a database server, you need to inform the network administrator so that person can make sure the information in these files is accurate.

The hosts file needs a single entry for each network-controller card that connects a computer running an Informix client/server product on the network. Each line in the file contains the following information:

Internet address (or ethernet card IP address)
Host name
Host aliases (optional)

Although the length of the host name is not limited in the hosts file, Informix limits the host name to 256 bytes. Table 9 includes a sample hosts file.

The services file contains an entry for each service available through TCP/IP. Each entry is a single line that contains the following information:

Service name
IBM Informix products use this name to determine the port number and protocol for making client/server connections. The service name can have up to 128 bytes.
Port number and protocol
The port number is the computer port, and the protocol for TCP/IP is tcp.

The operating system imposes restrictions on the port number. User informix must use a port number equal to or greater than 1024. Only root users are allowed to use a port number less than 1024.
Aliases (optional)

The service name and port number are arbitrary. However, they must be unique within the context of the file and must be identical on all computers that are running IBM Informix client/server products. The aliases field is optional. For example, a services file might include the following entry for a database server:

server2      1526/tcp

This entry makes server2 known as the service name for TCP port 1526. A database server can then use this port to service connection requests. Figure 6 includes a sample services file.

Important:

For database servers that communicate with other database servers, you must define a TCP/IP connection in DBSERVERNAME or DBSERVERALIAS even when both instances reside on the same machine.

For information about the hosts and services files, see your operating system documentation.

TCP/IP Connectivity Files on UNIX

On UNIX, the hosts and services files are in the /etc directory. The files must be present on each computer that runs an IBM Informix client/server product, or on the NIS server if your network uses Network Information Service (NIS).

Warning:

On systems that use NIS, the /etc/hosts and /etc/services files are maintained on the NIS server. The /etc/hosts and /etc/services files that reside on your local computer might not be used and might not be up to date. To view the contents of the NIS files, enter the following commands on the command line:

ypcat hosts 
ypcat services

TCP/IP Connectivity Files on Windows

You use information from the hosts and services network-configuration files to prepare the SQLHOSTS registry key for the TCP/IP network protocol. These files are in the following locations:

%WINDIR%\system32\drivers\etc\hosts
%WINDIR%\system32\drivers\etc\services

Alternately, you can configure TCP/IP to use the Domain Name Service (DNS) for host name resolutions. For information about these files, see your operating-system documentation.

The Dynamic Host Configuration Product (DHCP) dynamically assigns IP addresses from a pool of addresses instead of using IP addresses that are explicitly assigned to each workstation. If your system uses DHCP, you must also have installed Windows Internet Name Service (WINS). DCHP is transparent to the database server.

What Happens Between a Client and Server When a TCP/IP Connection Is Opened

When a TCP/IP connection is opened, the following information is read on the client side:

INFORMIXSERVER
hosts file information (INFORMIXSQLHOSTS, $INFORMIXDIR/etc/sqlhosts, the registry entry on Windows NT) and services file information
Other environment variables
Resource files

The following information is read on the server side:

DBSERVERNAME
DBSERVERALIAS
Server environment variables and configuration parameters, including any NETTYPE configuration parameter setting that manage TCP/IP connections
For more information about the NETTYPE configuration parameter, see NETTYPE Configuration Parameter and the IBM Informix Dynamic Server Administrator's Reference.

Multiple TCP/IP Ports

To take advantage of multiple ethernet cards, take the following actions:

Make an entry in the services file for each port the database server will use, as in the following example:
```
soc1         21/tcp
soc2         22/tcp
```
Each port of a single IP address must be unique. Separate ethernet cards can use unique or shared port numbers. You might want to use the same port number on ethernet cards connecting to the same database server. (In this scenario, the service name is the same.)
Put one entry per ethernet card in the hosts file with a separate IP address, as in the following example:
```
192.147.104.19          svc8
192.147.104.20          svc81
```
In the ONCONFIG configuration file, enter DBSERVERNAME for one of the ethernet cards and DBSERVERALIASES for the other ethernet card. The following lines show sample entries in the ONCONFIG file:
```
DBSERVERNAME chicago1
DBSERVERALIASES chicago2
```
In the sqlhosts file on UNIX or the SQLHOSTS registry key on Windows, make one entry for each ethernet card. That is, make an entry for the DBSERVERNAME and another entry for the DBSERVERALIAS.
```
chicago1 onsoctcp svc8 soc1
chicago2 onsoctcp svc81 soc2
```

After this configuration is in place, the application communicates through the ethernet card assigned to the dbservername that the INFORMIXSERVER environment variable provides.

IPX/SPX Connectivity Files (UNIX)

To configure the database server to use the IPX/SPX protocol on a UNIX network, you must purchase IPX/SPX software and install it on the database server computer. Your choice of IPX/SPX software depends on the operating system that you are using. For some operating systems, the IPX/SPX software is bundled with software products based on NetWare for UNIX or Portable NetWare. In addition, for each of the UNIX vendors that distributes IPX/SPX software, you might find a different set of configuration files.

For advice on how to set configuration files for these software products, consult the manuals that accompany your IPX/SPX software.