ID: Q185097
The information in this article applies to:
Some 3270 emulators, such as IBM's Personal Communications/3270, support SNA session-level compression that allows the 3270 data sent between the 3270 emulator and the host to be compressed. This compression is also known as Length-Checked Compression (LCC).
SNA Server 4.0 (and later) supports SNA session-level compression between the SNA Server and a Host (Mainframe or AS/400).
This feature allows the same type of data compression that is offered by those 3270 emulators that support SNA session-level compression, so it can be used in those instances where SNA session-level is needed.
SNA Server does not support SNA session-level compression (that is, LCC) for 3270 sessions across its native Function Management Interface ([FMI], also known as Emulator Interface Specification [EIS]). Compression is not supported across the FMI interface because the SNA Server service often has to segment the FMI data it receives from the 3270 emulator into smaller RUs to be sent to the host. If the data were compressed, SNA Server would not be able to properly segment the data.
In addition, SNA Server's LUA interfaces (RUI and SLI) do not support the ability to negotiate the use of SNA session-level compression.
The use of SNA session-level compression only needs to be used in certain instances. These may include the following:
- Slow link speeds between the SNA Server and the host. - Links whose costs are based on traffic volume.
In most cases, the link speed (that is, bandwidth) between the 3270 clients and the SNA Server is not slow enough to warrant the compression of the data between the client and the SNA Server.
IBM Personal Communications/3270 is manufactured by International Business Machines Corporation, a vendor independent of Microsoft; we make no warranty, implied or otherwise, regarding this product's performance or reliability.
Version : WinNT:2.11,2.11SP1,2.11SP2,3.0,3.0SP1,3.0SP2,3.0SP3,4.0
Platform : WINDOWS
Issue type : kbinfoLast Reviewed: August 11, 1998