Non-QDIO Open Systems Adapter
The awsosa device manager can emulate QDIO or non-QDIO operation. The mode is selected by the pathtype parameter in the device map (devmap). OSA-Express Direct (OSD) specifies a QDIO operation, and OSA-Express (OSE) specifies a non-QDIO operation. A non-QDIO operation is also known as an LAN Channel Station (LCS) operation or 3172 operation, although these descriptions are not exactly correct. A non-QDIO operation can involve TCP/IP, Systems Network Architecture (SNA), or both, although SNA usage is not tested or supported by Independent Software Vendor (ISV) IBM Z Program Development Tool (IBM zPDT) (ISV zPDT). Always use OSD mode unless you have a specific reason for using OSE mode. Multicast IP addresses are not supported for non-QDIO use.
IBM does not support Ethernet SNA operation for ISV zPDT, which means that problems or defects are not addressed by IBM if you attempt to use an SNA operation over Ethernet. However, some ISV zPDT users have worked with Ethernet SNA successfully. If you attempt this approach, consider the following information:
•The default Open Systems Adapter (OSA) Address Table (OAT) for the awsOSA device manager in LCS mode has TCP/IP at unit addresses 0 and 1. It has SNA only at unit address 2.
•Although SNA performance might be acceptable for simple testing, it is unlikely to be acceptable for heavier usage.
•A personal computer (PC) Ethernet adapter can be used for OSA-Express emulation in either QDIO or non-QDIO mode, but not both. The selection of QDIO or non-QDIO is made in the devmap definitions, and the awsosa device manager is used in both cases.
•The Open Systems Adapter/Support Facility (OSA/SF) tool is no longer available with z/OS and the partial replacement (QUERYINFO) is not functional for ISV zPDT. The effect is that the default OSE (non-QDIO) configuration (the OATs) of an emulated OSA cannot be easily changed.
•As a best practice, use OSD (QDIO) unless you have a specific requirement for OSE mode, and can work around the OSA/SF and QUERYINFO limitations.
When using the non-QDIO interface to the emulated OSA-Express2 function, the key parameters might look like the following example:
Devmap
[manager]
name awsosa 22 --path=F0 --pathtype=OSE
device E20 osa osa --unitadd=0
device E21 osa osa --unitadd=1
z/OS TCP/IP Profile
DEVICE LCS1 LCS E20 AUTORESTART
LINK ETH1 ETHERNET 0 LCS1
HOME 192.168.1.81 ETH1
...
BEGINRoutes
; Destination Subnet Mask FirstHop Link Size
ROUTE 192.168.1.0 255.255.255.0 = ETH1 MTU 1492
ROUTE DEFAULT 192.168.1.1 ETH1 MTU DEFAULTSIZE
ENDRoutes
...
START LCS1
This example assumes that z/OS contains an appropriate channel-to-channel (CTC) or OSA definition for addresses E20 and E21.1 Different addresses can be used, but they must match the IODF in your z/OS system. The HOME address and ROUTE statements in the example are only examples. The GATEWAY statements can be used instead of the ROUTE statements. The --unitadd parameter is used in the devmap because the default OSA unit addresses2 would be 20 and 21 (by using the two low-order digits of the device number), and we want unit addresses 0 and 1.3
Which mode should you use for OSA connectivity? QDIO mode has many benefits for TCP/IP usage on a larger IBM zSystems server, for example, it reduces the IBM zSystems workload and provides automatic sharing of the adapter across multiple logical partitions (LPARs). These considerations do not fully apply to an ISV zPDT system. The following points are relevant:
•The QDIO operation offloads some processing from the ISV zPDT CP to the Linux processor. The offloading is not as much as on a larger machine, but it helps. The QDIO operation also reduces the number of IBM zSystems server instructions that are needed to maintain LAN I/O operation. In informal operation, we noticed that FTP performance was about 20% faster with QDIO than with LCS.
•QDIO operation is only for TCP/IP because it does not handle SNA. QDIO can provide VSWITCH, IPv6, and Enterprise Extension connections.
•Non-QDIO operation can mix TCP/IP and SNA if you want. However, SNA operation with ISV zPDT is not supported.
•Suitable non-QDIO (LCS) devices are defined in z/OS Application Development Controlled Distribution (ADCD) systems. (These systems are the CTCs starting at address E20.)
Other than these points, there is no practical difference between using QDIO or non-QDIO on an ISV zPDT system. In particular, the user at a TN3270 Time Sharing Option (TSO) session cannot detect the difference. Normal TCP/IP functions, such as FTP and Telnet, do not detect any differences.
1 Local area network (LAN) operation in LCS mode can use CTC definitions in the z/OS IODF. This function is a carryover from earlier LAN implementations.
2 This unit address is the (emulated) hardware address within the (emulated) OSA control unit. It is not the device number (“address” in common terminology).
3 The default OAT that is used by OSA requires unit addresses 0 and 1 for TCP/IP when in OSE mode.
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