ERROR DESCRIPTION:
Cannot reconnect an SDLC line after switching to a Backup. Trace
on both sides shows one sending XID over and over but it doesn't
reach the other side. SNACOM should act as follows:
 - forward a CLOSE STATION indication to VTAM only when a FID4
   XID is received by the secondary
 - don't reset the secondary link inactivity timer when any
   XID is received by a secondary in the link opened state
   (and let the link inactivity expiration drive the CLOSE
   STATION indication to VTAM).
One side, or both, of the line may hang in PCTD1. Vary Act,
followed by Vary Inact on either side changes nothing.

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TO INSTALL THE APAR:

 1. FROM AN OS/2 window on the 3172, CD to
    IBMCOM\PROTOCOL directory.
 2. Rename DESDLC.OS2 and DESDLC.MAP(if it exists)
    to something else for backup.
 3. Put DESDLC.OS2 & DESDLC.MAP into the Directory
    IBMCOM\PROTOCOL
 4. Shutdown and IPL the 3172.