SLI Libraries Set Wrong RU Size After Unbind(Hold) (162592)

SYMPTOMS

Some 32-bit SLI applications may fail when you try to transfer large amounts of data. Investigation shows that the SNA RUI layer is returning an error code of DATA_TRUNCATED when performing a RUI_READ of more than 256 bytes.

CAUSE

There is a problem the SLI library such that it is not picking up the RU size correctly on successive BINDs. When the SLI library receives a BIND, followed by UNBIND(HOLD) and then a new BIND, the SLI library posts an RUI_READ of 256 bytes, even though 3840 byte RUs were negotiated in the final BIND.

So, when an RU arrives on the session which is larger than 256 bytes, the SLI_RECEIVE posted only receives 256 bytes and gets a DATA_TRUCATED error from the underlying RUI libraries and the SLI application only gets the first 256 bytes of the host application message.

Following is an illustration of the data flow involved:

SNA Server              Host
----------              ----

   <------------------- BIND ("NMP" session manager),
                        SLU receive size = "85"(256)

BIND +RSP --------------------------->
      <logon>

<---------------------- UNBIND(Hold)

UNBIND +RSP ---------------------->

   <------------------- BIND (Host SLI application),
                        SLU receive size = "F8" (3840)

BIND +RSP -------------------------->

   <RUI_READ only reads 256 bytes >

RESOLUTION

Apply the update to SNA Server 2.11 Service Pack 1 and SNA Server 3.0 that corrects this problem. The updated module is Winsli32.dll.

VTAM programmers will be able to work around this problem by configuring their session manager (NMP) to send a BIND to SNA Server that specifies a PLU send size of "F8" (this is set in Byte 11 of the BIND message).

NOTE: This is NOT the BTU size, but MAXDATA if configured in the LU definition or RUSIZE if configured in the MODETAB for the LU-LU session (or the NMP host session manager application).

STATUS

Microsoft has confirmed this to be a problem in the Microsoft products listed at the beginning of this article. A supported fix is now available, but has not been fully regression-tested and should be applied only to systems experiencing this specific problem. Unless you are severely impacted by this specific problem, Microsoft recommends that you wait for the next Service Pack that contains this fix. Contact Microsoft Technical Support for more information.

MORE INFORMATION

The following is an LUA API trace of a large RUI_READ demonstrating the failure.

 SLI    ---------------------------------------------- 11:28:10.32
 SLI    SLI_RECEIVE request
 SLI    ---- Verb Parameter Block at address 0080FD68 ----

Data omitted for brevity.
In the VCB an lua_max_length of 4K assigned.
NOTE: VCB structure is packed.

 SLI
 SLI    ---------------------------------------------- 11:28:10.61
 SLI    SLI_RECEIVE response
 SLI    IN_PROGRESS - OK
 SLI    ---- Verb Parameter Block at address 0080FD68 ----

Data omitted for brevity.

SLI
 RUI    ---------------------------------------------- 11:28:12.73
 RUI    RUI_READ response
 RUI    UNSUCCESSFUL - DATA_TRUNCATED

Data omitted for brevity.
In the VCB the lua_max_length(offset 35(2 byte field)) and
lua_data_length(offset 37(2 byte field)) fields have a value of 256 bytes.

 RUI