Compressing Data Over a Network


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The BEA Tuxedo system allows you to compress data being sent from one application process to another. Data compression is useful in most applications and is vital in supporting large configurations. You can use data compression when the sender and receiver of a message are on the same machine (local data compression), or when the sender and receiver of a message are on different machines (remote data compression). Both forms of compression provide advantages:

Because messages are sent over interprocess communication (IPC) queues, the advantage of local data compression is that it results in lower utilization of IPC resources.
Because messages are sent over a network, the advantage of remote data compression is that it results in lower utilization of network bandwidth.

How to Set the Compression Level

If you decide to use data compression, you must set the CMPLIMIT parameter in the MACHINES section of the configuration file, as follows:

CMPLIMIT=string_value1[,string_value2]

The strings that make up the value of this parameter specify the threshold message size for messages bound to remote processes (string_value1) and local processes (string_value2). Only the first string is required. The default for both strings is the value of the MAXLONG parameter.

In addition, you have the option of setting the TMCMPPRFM parameter to establish an appropriate balance between compression and CPU performance. Higher and slower compression results in more efficient network bandwidth; lower but faster compression yields less CPU utilization.

To specify the desired level of compression, complete the following procedure.

Set the compression threshold using the CMPLIMIT parameter in the UBBCONFIG configuration file.
(Optional step) Set the TMCMPPRFM environment variable. The value of TMCMPPRFM must be a single digit between 1 and 9; the default is 1.
A value of 1 specifies the lowest level of compression with the fastest performance; 9 represents the highest level of compression with the slowest performance. The lower the number, the more quickly the compression routine is executed.

For more information on setting the TMCMPPRFM variable, refer to tuxenv(5) in the File Formats, Data Descriptions, MIBs, and System Processes Reference.

Selecting Data Compression Thresholds

You can designate a compression threshold for messages: any messages larger than the threshold you specify are compressed. To designate a compression threshold, set the CMPLIMIT parameter. For instructions, see How to Set the Compression Level.

When choosing data compression thresholds, keep in mind the following criteria:

Consider using remote data compression if your sites are running BEA Tuxedo release 4.2.1 or later. Your setting depends on the speed of your network. You may want to assign different settings, for example, to an Ethernet network (which is a high-speed network) and an X.25 network (which is a low-speed network).
- For a high-speed network, consider setting remote data compression to the lowest limit for file transfers generated by the BEA Tuxedo system. (See the note about file transfers provided later in this list.) In other words, compress only messages that are large enough to be candidates for file transfer on either the sending site or the receiving site. Note that each machine in an application may have a different limit. If this is the case, choose the lowest limit possible for each machine.
- For a low-speed network, consider setting remote data compression to zero on all machines; that is, compress all application and system messages.
Consider using local data compression for sites running BEA Tuxedo release 4.2.1 or later, even if they are interoperating with pre-release 4.2.1 sites. This results in lower utilization of IPC resources. This setting also enables you to avoid file transfers in many situations that might otherwise require a transfer and, when file transfers cannot be avoided, this setting greatly reduces the size of the files used. For more information, refer to Message Queues and Messages in Installing the BEA Tuxedo System.
For local data compression, you can assign a different threshold to each machine in an application. If this is the case, always choose the lowest limit possible for each machine.

Note: For high-traffic applications that involve a large volume of timeouts and discarding of messages due to IPC queue blocking, you may want to lower the demand of the application on the IPC queuing subsystem by having local compression done at all times.

Because compression depends on the type of data being transmitted, we strongly recommend that you try different settings in your environment to determine which one yields the best results.