![CommBufferSize connection parameter [CBSIZE]](gif/backward.gif)
Specifies client-side network protocol options.
Anywhere. The CommLinks (LINKS) connection parameter is optional for connections to a personal server, and required for connections to a network server.
String
Use only the shared memory communication protocol to connect.
If you do not specify a CommLinks (LINKS) connection parameter, the client searches for a 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 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 one or more protocols in the CommLinks (LINKS) connection parameter, the client uses the named communication protocol(s), in the order specified, to search for a network database server. Note that if shared memory is specified, an attempt to connect using shared memory is made first, and then the remaining communication protocols are tried in the order in which they are specified. A connection error appears and the connection attempt aborts if the connection fails to connect using a specified protocol, even if there are protocols remaining in the list to try.
CommLinks (LINKS) connection parameter values are case insensitive, and include:
SharedMemory (ShMem) Start the shared memory protocol for same-computer communication. This is the default setting. The client tries shared memory first if it is included in a list of protocols, regardless of the order in which protocols appear.
ALL Attempt to connect using the shared memory protocol first, followed by all remaining and available communication protocols. Use this setting if you are unsure of which communication protocol(s) to use.
TCPIP (TCP) Start the TCP/IP communication protocol. TCP/IP is supported on all operating systems.
SPX Start the SPX communication protocol. The SPX protocol is supported for Windows and NetWare clients.
Each of these values can have additional network protocol options supplied.
You may want to use a specific protocol, as opposed to ALL, for the following reasons:
The network library starts slightly faster if the client uses only necessary network protocols.
Connecting to the database may be faster.
You must specify the protocol explicitly if you want to tune the broadcast behavior of a particular protocol by providing additional network protocol options.
The CommLinks (LINKS) connection parameter corresponds to the database server -x option.
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 link and searches for the server on the local network. If that fails, it starts the SPX link and searches for the server over SPX.
CommLinks=tcpip,shmem,spx
The following connection string fragment starts the SPX port and searches for the server over SPX. If the search fails, it then starts the TCP link and searches for the server on the local network, as well as the host kangaroo. Note that if the server is found over SPX, the TCP link is not started.
CommLinks=spx,tcpip(HOST=kangaroo)