Why is FTP using sysplex distributor slower than FTP using DNS/WLM?

By default, when using sysplex distributor, traffic from the distributing system to the target system uses the XCF links. For bulk transfers of data (especially FTP for transfers to the z/OS system), this results in very slow performance and increased CPU usage in the TCP/IP address space.

To speed up your FTP PUTs significantly when using sysplex distributor, you need to enable VIPAROUTE, which forces data transfer for FTP PUTs and other high-volume transfers to use OSA.

To enable VIPAROUTE, you need to specify the following in the VIPADYNAMIC section of the distributing stack's TCP/IP PROFILE:

VIPAROUTE dynxcfip target_ipaddr
where:
dynxcfip is the IPv4 or IPv6 dynamic XCF address which uniquely identifies the target stack

See the section about VIPAROUTE in the IP Configuration Reference.

A VIPAROUTE statement (in the TCP/IP PROFILE) defines a route from a distributing stack or a backup distributing stack to a target stack. For example:

VIPAROUTE DEFINE 10.1.1.5 10.50.10.1

This statement specifies that traffic (within the sysplex) from 10.1.1.5 to 10.50.10.1 should be handled by the VIPAROUTE function, which selects the most appropriate route at that instant.

The command NETSTAT VIPADYN /-v may be used to query the status of a dynamic VIPA, including the usage of VIPAROUTE; for example:

 MVS TCP/IP NETSTAT CS V1R9 TCPIP Name: TCPIPC 11:24:56
 Dynamic VIPA:IpAddr/PrefixLen: 10.20.20.1/28
 Status: Active Origin: VIPADefine DistStat: Dist/Dest
 VIPA Route:
 DestXCF: 10.1.1.5
 TargetIp: 10.50.10.1
 RtStatus: Active

Suggestion: For multiple LPARs on the same processor complex, consider defining a HiperSockets channel referenced by the IQDCHPID VTAM start option instead of a VIPAROUTE for those neighboring systems.