CompressionThreshold (COMPTH) connection parameter

Syntax

{ CompressionThreshold | COMPTH }=size[ k ]

Usage

Anywhere except TDS. Only applies to compressed connections.

Allowed values

• size – This integer specifies the size limit at which packets are compressed. The default value is in bytes, but you can use k to specify units of kilobytes. If both the client and database server specify different compression threshold settings, the client setting applies. The minimum supported value is 1 byte, and the maximum supported value is 32767 bytes. Values less than 80 bytes are not recommended.

Default

120

If no CompressionThreshold value is set, the compression threshold value is controlled by the setting on the server, which defaults to 120 bytes.

Remarks

Changing the compression threshold can help performance of a compressed connection by allowing you to only compress packets when compression will increase the speed at which the packets are transferred.

When compression is enabled, individual packets may or may not be compressed, depending on their size. For example, SAP Sybase IQ does not compress packets smaller than the compression threshold, even if communication compression is enabled. As well, small packets (less than about 100 bytes) usually do not compress at all. Since CPU time is required to compress packets, attempting to compress small packets could actually decrease performance.

Lowering the compression threshold value may improve performance on very slow networks, while raising the compression threshold may improve performance by reducing CPU. However, since lowering the compression threshold value will increase CPU usage on both the client and server, a performance analysis should be done to determine whether changing the compression threshold is beneficial.