Eicon Networks CX1 Dokumentacja Pobierz pdf (Strona 62)

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Communications Device Drivers

Section 5 - General Configuration and Usage Information

Page 212

cfSOFTWARE Confidential,

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5.16 LU6.2 Configuration (continued)

Pacing

Proper pacing in an SNA network is important to prevent congestion and buffer overflow errors. In SNA

configurations without much LU6.2 activity, certain default pacing values may be set that can cause problems.

LU6.2 sessions are capable of generating very large quantities of traffic in a single direction without responses

from the receiver. By contrast, the typical terminal session will never send more than one screen’s worth of data

at a time.

Pacing is controlled at several levels, and is a generally complex topic. The IBM VTAM Network

Implementation Guide provides a detailed overview of pacing.

By setting the three pacing values in the mode definitions and the VPACING value on the APPL definition, to

relatively small (non-zero) numbers (we suggest three as a starting point), are limiting total activity to a modest

number of parallel sessions, all congestion and buffer overflow problems should be avoided. Setting small

pacing values will, however, adversely affect performance. Running with large pacing values or running many

simultaneous sessions requires careful attention to pacing and buffer space availability.

By default

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LU6.2 drivers, in conjunction with APPX, perform an internal pacing function

which limits the amount of unacknowledged data sent to the host. Usually this limit is twenty (20) data blocks

(usually 2-4KB). This may be overridden by the application or in MAINCON. Even without any SNA pacing,

the pacing performed by APPX will usually suffice for a modest number of parallel sessions.

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Eicon Networks CX1 Dokumentacja Strona 62