Configuring Shared Memory Communications - Direct Memory Access

Use these steps to configure and begin to use Shared Memory Communications - Direct Memory Access (SMC-D).

Perform the following steps to configure SMC-D:

1. If you are using IPv4 IPAQENET DEVICE, LINK, and HOME definitions, convert them to INTERFACE definitions. SMC-D processing is provided for only OSD interfaces that are configured with INTERFACE definitions. For more information about converting IPv4 IPAQENET DEVICE, LINK, and HOME definitions to INTERFACE definitions, see Steps for converting from IPv4 IPAQENET DEVICE, LINK, and HOME definitions to the IPv4 IPAQENET INTERFACE statement.
2. If you are using IPv4 IPAQIDIO DEVICE, LINK, and HOME definitions, convert them to INTERFACE definitions. SMC-D processing is provided for only HiperSockets™ interfaces that are configured with INTERFACE definitions. For more information about converting IPv4 IPAQIDIO DEVICE, LINK, and HOME definitions to INTERFACE definitions, see Steps for converting from IPv4 IPAQIDIO DEVICE, LINK, and HOME definitions to the IPv4 IPAQIDIO INTERFACE statement.
3. Configure the SMCD parameter on the GLOBALCONFIG statement in the TCP/IP profile. The SMCD parameter includes the following subparameters:
   • FIXEDMEMORY specifies the total amount of memory, in megabytes, that can be used for the direct memory buffers. The default value is 256 MB.
   • TCPKEEPMININTERVAL specifies the minimum time interval, in seconds, for sending keepalive probes for TCP connections that use SMC-D protocols to exchange data. The default value is 300 seconds. For more information, see TCP keepalive.
   For more information about SMCD subparameters on the GLOBALCONFIG statement, see z/OS Communications Server: IP Configuration Reference.
4. (Optional) Configure the SMCD parameter on the IPAQENET and IPAQENET6 INTERFACE statements with the OSD channel path ID type (CHPIDTYPE OSD).
   Tip: SMCD is the default setting on the IPAQENET and IPAQENET6 INTERFACE statements for the OSD CHPID type.
   Guideline: If you enable Multipath and the equal-cost interfaces are associated with different IP subnets, enabling SMC for some of, but not all, the interfaces can cause unpredictable SMC usage. You must specify either SMCD or NOSMCD on all equal-cost interfaces.
5. (Optional) Configure the SMCD parameter on the IPAQIDIO and IPAQIDIO6 INTERFACE statements.
   Tip: SMCD is the default setting on the IPAQENET and IPAQENET6 INTERFACE statements.
   Guideline: If you enable Multipath and the equal-cost interfaces are associated with different IP subnets, enabling SMC for some of, but not all, the interfaces can cause unpredictable SMC usage. You must specify either SMCD or NOSMCD on all equal-cost interfaces.
6. Associate the interfaces with the appropriate subnet or prefix.
   • For an IPv4 interface to be eligible for SMC-D, you must configure a nonzero subnet mask on the INTERFACE statement in the TCP/IP profile.
     Result: SMC-D is used only between peers whose interfaces have the same subnet value.
   • For an IPv6 interface to be eligible for SMC-D, the interface must have at least one prefix that is associated with it.
     Rule: A prefix can be associated to an IPv6 interface in any of these ways:

     • A prefix that is received on a router advertisement message from an attached router
     • A prefix that is configured in OMPROUTE by using the PREFIX parameter on the IPV6_OSPF_INTERFACE, IPV6_RIP_INTERFACE, or IPV6_INTERFACE statement
     • A direct static prefix route that is configured over the interface on a ROUTE statement in a BEGINROUTES block in the TCP/IP profile
     Result: SMC-D is used only between peers whose IPv6 interfaces have at least one prefix in common.
7. If you use VLANs for your SMC-D communications, configure the VLANID parameter on the IPAQENET and IPAQENET6 INTERFACE statements for the OSD CHPID type and on the IPAQIDIO and IPAQIDIO6 INTERFACE statements. For more information, see VLANID considerations.
8. If you have a server application that primarily uses short-lived TCP connections, you might avoid SMC-D rendezvous processing for TCP connections that are using that server port. Configure the NOSMC parameter on the PORT or PORTRANGE statement for the server port or ports that this server application uses. For more information, see z/OS Communications Server: IP Configuration Reference.
9. Start the IPAQENET and IPAQENET6 interfaces, or the IPAQIDIO and IPAQIDIO6 interfaces. When the first SMC-D capable OSD or HiperSockets interface becomes active for a given physical network ID (PNetID), z/OS® Communications Server automatically looks for an available ISM device with a PNetID value that matches the PNetID value of the OSD or HiperSockets interface. If a matching ISM device is available, VTAM® activates the ISM device and provides the associated PFID to the TCP/IP stack. For more information about PNetIDs, see Physical network considerations.