GetFile transfers sometimes fail with an
XCM0889 fatal TCP/IP failure in XCOMS during state confirm header. Primary RC=16 Sec=0 TXPI 217 rc=3426.
When the transfer retries, it will generally succeed the 2nd or 3rd time.
In this case the transfers are failing because they have exceeded the limits of the MAXCLIENTS and MAXBACKLOG parameters set when bringing up the XCOM TCPIP server. When retried when the server is less busy, the transfer will succeed.
The XCOM TCPIP server is started with a default number of 2 MAXCLIENTS ("slaves") and 5 MAXBACKLOG. This allows two concurrent transfers with 5 waiting transfers = 7 maximum transfers. Two "slaves" will handle two concurrent TCPIP transfers. If more TCPIP transfers come in when 2 TCPIP transfers are already active, they will wait unless the number of waiting transfers exceeds the number specified for MAXBACKLOG. If this is also exceeded, then the XCOM0889 error message shown above will be displayed and the transfer will fail.
The MAXCLIENTS and MAXBACKLOG parameters should be tuned for your environment. The total of MAXCLIENTS + MAXBACKLOG should be greater than the total number of transfers that will be active at any one time in order to prevent having transfers fail with this message.