CFT z/os & TCP/IP - how to set the best parameter values for the best performances

Ensure the TCP parameters value TCPSENDBFRSIZE and TCPRECVBFRSIZE are set to at least 32768 or higher

Ensure CFT protocols used for TCP/IP transfers are set with RRUSIZE = 32000, SRUSIZE = 32000 ) or higher.

Note: Transfer CFT z/OS accepts CFTPROT xRUSIZE values less than or equal to 65,000 bytes.
A high RUSIZE value significantly reduces the CPU load:
for example, the load is reduced by 30% when you change from 4 k to 16 k. Since CFTPROT values are negotiated with the remote side and the smallest value is used, it is a good performance choice to specify large values for CFTPROT RRUSIZE and RPACING, but do not set RCHKW to 0 or above 2 (1 or 2 is the right choice).

Some internal bench:

· When TCPSNDBUF=16K
RUSIZE CFTTFIL CFTTPRO CFTTCP
4056 40 159 179
8192 30 112 105
12288 29 95 86
16380 29 86 73
32000 29 85 72

Time is in seconds.
CPU consumption for CFTTPRO/CFTTCP varies in inverse proportion to the RUSIZE value.

· When TCPSNDBUF=64K :
RUSIZE CFTTFIL CFTTPRO CFTTCP
32000 29 85 59