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z/OS Communications Server and OSA Interoperability Maintenance
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Abstract
z/OS Communications Server R170, R180, R190, and R1A0 are shipped with support for Segmentation Offload. z/OS Communications Server R160 requires PK02490 and OA11148 for this new function. In all cases, OSA-Express2 or OSA-Express3 cards are required to enable segmentation offload.
 
Content
TCP Segmentation Offload (also called Large Send) transfers the overhead of segmenting outbound data into individual TCP packets to the QDIO (Queued Direct I/O) attached OSA-Express2 device. Offloading segmentation of streaming type workloads reduces CPU utilization and increases throughput.

If you have the OSA hardware:
    OSA-Express2 1000BaseT (#3366)
    OSA-Express2 Gigabit SX (#3365)
    OSA-Express2 Gigabit LX (#3364)
    OSA-Express2 10 Gigabit LR (#3368)
    OSA-Express3

and
    R160 with PK02490/UK04060/UK04601 and OA11148/UA18116
      or
    Base R170 or R180 or R190 or R1A0

then,
    you are susceptible to poor performance , VTAM INOP errors, or both.

    Example of VTAM INOP errors:

    IST1222I DATA DEVICE xxxx IS INOPERATIVE, NAME IS nnnnn
    IST1578I DEVICE INOP DETECTED FOR nnnnn BY ISTLLCWC CODE = 100

MINIMUM COMMUNICATIONS SERVER MAINTENANCE

    NOTE: Even with the following maintenance applied, the recommendation is to disable the segmentation offload feature unless a supported microcode level is installed. See the table in the MINIMUM OSA MICROCODE LEVELS section.

    NOTE: APAR PK21685 for R160 and R170 and PK26905 for R180 added a configurable option to disable the segmentation offload function.
    NOTE: APAR PK46334 for R160 , R170,and R180 changed the default for segmentation offload to disabled. The apar for R190 is PK47376. Segmentation Offload is disabled by default in R1A0.
      - or -
      - or -


MINIMUM OSA MICROCODE LEVELS


Processor Model
EC Driver
LIC Bundle
EC Stream
    MCL
OSA Code Level
z/890 (2086)
z/990 (2084)
55K
121
J13476
023
0.2C
z/9 - BC (2096)
z/9 - EC (2094)
63J
upgrade to Driver 67L
67L
36A
G40946
007
8.81
z/10 - EC (2097)
z/10 - BC (2098)
73G
N/A
F85892
(OE2)
N/A
Not Currently Available on OSA Express 2
40A
F85897
(OE3)
010
0.1A
76D
10B
N10953
(OE2)
001
3.03
2A
N10959 (OE3)
001
7.07

Additional information can be found in the appropriate processor PSP bucket and hardware tip TDR H194022.

If you have any further questions, please contact your CE.
    VERIFICATION STEPS
      You can also verify the OSA microcode level from VTAM command DISPLAY NET,TRL,TRLE=xxxxx. The output will contain the following line: IST1716I PORTNAME = xxxxxx LINKNUM = 0 OSA CODE LEVEL = 0881
        NOTE: In this example, the Level is for a z/9.

      You can verify that segmentation offload is enabled on the stack via the NETSTAT CONFIG command. The output will include the following lines: Global Configuration Information: .... SegOffload: Yes SysplexWLMPoll: 060

      You can verify that Segmentation Offload is actually in use from the NETSTAT DEVLINK command. The output for the OSAs will contain the line: CHECKSUMOFFLOAD: YES SEGMENTATIONOFFLOAD: YES
        NOTE: If this line does not appear in the output, Segmentation Offload is not available.
     
     
    		 

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    Document information
     Product categories:
     Software
     Networking
     Enterprise Connectivity
     z/OS Communications Server
     All
     Operating system(s):
      z/OS
     Software version:
      1.6, 1.7, 1.8, 1.9, 1.10
     Software edition:
      All Editions
     Reference #:
      1232599
     IBM Group:
     Software Group
     Modified date:
     2009-03-12

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