Joined: 06 Jun 2008 Posts: 8188 Location: East Dubuque, Illinois, USA
Googling exci reason=606 returns a number of hits, one of which on the first page has this:
A VERIFY call to the MVS™ subsystem interface (SSI) to obtain the current CICS® SVC number failed.
The Initialize_User request is terminated. The return code from the SSI call is returned in subreason field-1 of the return area. This error occurs before the external CICS interface dump services are initialized, therefore EXCI issues an MVS user abend (0405) to force a SYSMDUMP.
Locate the return code in the dump, and use this with the rest of the dump and SSI documentation to determine why the VERIFY request failed. When the problem is resolved, restart the client application program.
Parent topic: Reason codes for response: SYSTEM_ERROR
I don't know why you don't think this is specific enough.
Contact your site support group and have them check on the CICS SVC. Or, you could be attempting to provide the wrong SSI ....