Chapter 3. Operating NetView FTP V2.2.1 MVS - IBM

Rules for Defining Pacing Values in a Logon Mode Table
When defining your pacing values, you should follow these general rules:
� To permit pacing control, always define a logon mode table entry for all servers
at all locations where NetView FTP is installed.
� Always set SSNDPAC to a nonzero value.
� Set PSNDPAC and SRCVPAC to zero.
� Always define VPACING in your APPL definition statements.
By using these rules, you ensure that a server paces all data transfers as specified
in the VPACING operand in the APPL statement. This permits you to make simple
changes to pacing values without having to assemble and link-edit the logon mode
table again.
Note: If no session parameters are found via the default logon mode table entry,
NetView FTP V2.2.1 MVS sets all pacing fields to zero in the BIND image that it
creates.
Machine Cycles versus Transfer Time
Normally, the limiting factor in performance is the transfer time on the line rather
than the number of cycles used by the processing unit to process the data.
For example, assume that NetView FTP V2.2.1 MVS is transferring 120-character
records and that it is compressing each one to about 100 characters. Assuming an
RU size of 1KB and a telecommunication link that operates at 9600 bits per second
(about 1200 bytes per second), it takes slightly less than one second to transfer the
block of data.
In fast processing units, the data could become available much faster than the line
can handle it, unless the line is extremely fast. Normally, the way to improve performance
when using NetView FTP V2.2.1 MVS would be to examine those
aspects that could improve the transfer time, such as the introduction of faster
lines, more lines (that is, use of transfer groups), increase of pacing value,
reduction of contention on lines, and increase of RU size.
Simultaneous File Transfers per Server versus Several Servers
The system administrator must carefully consider the file transfer workload:
� When a particular file is to be transferred.
� The size of the files to be transferred.
� Subsequent job dependencies.
The file transfer should be classified, that is, a server class is to be given for each
file transfer, for example:
Class 0 Default class
Class T Tape mount required
Class L Long runtime, large datasets
Class S Short runtime, small datasets
214 NetView FTP V2 MVS Installation, Operation, and Administration