{ CommLinks | LINKS }={ [ SharedMemory | ShMem ] | ALL | [ TCPIP | TCP ] } [, ... ] string

Anywhere. The CommLinks (LINKS) connection parameter is optional for connections to a personal server, and required for connections to a network server.

CommLinks (LINKS) connection parameter values are case insensitive, and include:

Each of these values can have additional network protocol options supplied. See Network protocol options.

Use only the shared memory communication protocol to connect.

If you do not specify a Host connection parameter or a CommLinks (LINKS) connection parameter, the client searches for a database server on the current computer only, and only using a shared memory connection. This is the default behavior, and is equivalent to CommLinks=ShMem. The shared memory protocol is the fastest communication link between a client and database server running on the same computer, as is typical for applications connecting to a personal database server.

For information about securing shared memory connections on Unix, see Security tips.

If you specify CommLinks=ALL, the client searches for a server using all available communication protocols. Since there may be an impact on performance if you specify CommLinks=ALL, use this setting only when you don't know which protocol to use.

If you specify both TCPIP and SharedMemory, shared memory is attempted first, followed by TCP/IP if the database server cannot be found over shared memory. Shared memory is attempted first, even if TCP/IP is specified first.

The CommLinks (LINKS) connection parameter corresponds to the -x database server option.

If you specify multiple settings for the same connection parameter, then the last value specified is the one that is used. For example, in the following connection string, both shared memory and TCP/IP are specified. In this case, TCP/IP is used because it was specified later in the string.

"UID=DBA;PWD=***;Server=demo;START=d:\sa12\bin64\dbsrv12.exe 
-x tcpip(port=3277);DBN=demo;DBF=d:\sa12\samples\demo.db;LINKS=SHMEM;ENC=none;
CommLinks=tcpip(HOST=localhost)"

The Host connection parameter is an alias to several existing TCP/IP options. In most cases you should not need to use the LINKS connection parameter. Because the host name is required, but the port number and ServerName connection parameter are optional, there are four possible combinations:

• Host connection parameter
• Network protocol options
• Client/server communications
• -x dbeng12/dbsrv12 server option
• Using connection parameters
• Server name caching for faster connections
• CommLink connection property

The following connection string fragment starts the TCP/IP protocol only:

CommLinks=tcpip

The following connection string fragment starts the shared memory protocol and searches for the database server over shared memory. If the search fails, it then starts the TCP/IP protocol and searches for the server on the local network.

CommLinks=tcpip,shmem

The following connection string fragment starts the shared memory protocol and searches for the server over shared memory. If the search fails, the TCP protocol is started and it searches for the server on the local network, and the host kangaroo. Note that if the server is found over shared memory, the TCP link is not started.

CommLinks=shmem,tcpip(HOST=kangaroo)