Sybase DC38133-01-0902-01 manual Encoding and compressing messages, Encoding scheme

Chapter 10. SQL Remote Administration

Encoding and compressing messages

As messages pass through e-mail and other message systems, there is a danger of them becoming corrupted. For example, some message systems use certain characters or character combinations as control characters.

Message size affects the efficiency with which messages pass through a system. Compressed messages can be processed more efficiently by a message system than uncompressed messages. On the other hand, carrying out compression can itself take a significant amount of time.

SQL Remote encoding	SQL Remote has a message encoding and compression scheme built in to
and compression	the Message Agent. The scheme provides the following features:
	♦ Compatibility	The system can be set up to be compatible with previous
	versions of the software.
	♦ Compression	You can select a level of compression for your messages.
	♦ Encoding SQL Remote encodes messages to ensure that they pass
	through message systems uncorrupted. The encoding scheme can be
	customized to provide extra features.
Settings for compatibility	To be compatible with previous versions of the software, you should set the
	database option COMPRESSION to be -1 (minus one) at each database
	running the Version 6 software. This setting ensures that messages are sent
	out in a format compatible with older versions of the software.
Upgrading SQL Remote	If you upgrade the consolidated database Message Agent first, you should
	set its COMPRESSION database option to -1. As each remote site in your

replication system is upgraded to Version 6, you can change its setting of the COMPRESSION option to a value between 0 (no compression) and 9 (maximum compression). This allows you to take advantage of compression features on messages being sent to the consolidated database. Once all remote sites are upgraded, you can set the consolidated site Message Agent COMPRESSION option to a value other than -1.

In addition, setting COMPRESSION to a value other than -1 allows you to take advantage of the Version 6 message encoding improvements.

The encoding scheme

The default message-encoding behavior of SQL Remote is as follows:

♦For message systems that can use binary message formats, no encoding is carried out.

235