Diagnosing problems with Shared Memory Communications
Shared
Memory Communications (SMC)
problems are often related to switch configuration, VLAN connectivity, physical network ID (PNetID)
configuration, and other configuration issues.
Common problems with using SMC include the following categories:or SMCD field of the Netstat DEvlinks/-d report provide information that is
related to SMC
problems. The SMCR field applies to Shared Memory
Communications over Remote Direct Memory Access (SMC-R) processing, and the SMCD field applies to
Shared Memory Communications - Direct
Memory Access (SMC-D) processing.
SMC include the following categories:- SMC-R switch configuration issues
- SMC-R VLAN configuration issues
- SMC-D VLAN connectivity issues
- Physical network ID configuration issues
- No associated subnet mask
- PFID status remains STARTING
- Problem with SMC interaction with security function
or SMCD field of the Netstat DEvlinks/-d report provide information that is
related to SMC
problems. The SMCR field applies to Shared Memory
Communications over Remote Direct Memory Access (SMC-R) processing, and the SMCD field applies to
Shared Memory Communications - Direct
Memory Access (SMC-D) processing.For a complete list of SMCReason codes in the Netstat ALL/-A report and the SMCR or SMCD Disabled reasons in the Netstat DEvlinks/-d
report, see z/OS Communications Server: IP System Administrator's Commands.
- SMC-R switch configuration issues
Remote Direct Memory Access (RDMA) processing requires standard 10 GbE switch support, and distance limitations might exist. Enable the global pause frame (a standard Ethernet switch feature for Ethernet flow control that is described in the IEEE 802.3x standard) on the switch. - SMC-R VLAN configuration issues
The SMC-R VLAN configuration checklist is provided for you to verify that your VLAN environment for RoCE, and therefore for SMC-R, is correctly configured. - SMC-D VLAN connectivity issues
Internal shared memory (ISM) processing does not require network switches. However, VLANs are supported over ISM devices to allow for separation of traffic. The OSD or HiperSockets VLAN attributes propagate to the associated ISM interfaces that use the same physical network ID (PNetID). - Physical network ID configuration issues
The TCP/IP stack must be able to determine which physical network is connected to a particular IBM 10 GbE RoCE Expressor internal shared memory (ISM) interface, so that
the 10 GbE RoCE Express
or ISM interface can be associated with the SMC capable interfaces that connect to that same physical
network. - No associated subnet mask
Shared
Memory Communications (SMC) is used only between peers whose IPv4 interfaces have the same
subnet value or whose IPv6 interfaces have at least one prefix in common. - PFID status remains STARTING
The PFIDSTATUS field is the Peripheral Component Interconnect Express (PCIe) function ID (PFID) status for the RNIC or the internal shared memory (ISM)
interface. - Problem with SMC interaction with security function
Generally, security functions that require TCP/IP to examine TCP packets cannot be used withSMC
communications because data that is sent over SMC links is not converted into TCP packets.
Parent topic: Diagnosing z/OS Communications Server components