reset of UCB entries

I am trying to back up a file with adabck and get Backup Failed with 255
adaopr db=xx display=UCB shows one entry as follows:
Date/Time Entry Id Utility Mode Files
--------- -------- ------- ---- -----
25-APR-2014 14:57:20 9084 adabck ACC 126
Even though file 126 is not the one that I am attempting to back up, I thought that I would try to remove it.
I tried adaopr, db=xx reset=ucb,ident=9084 as well as other commands with no success.
I then stopped and restarted the nucleus hoping it would clear out the UCB, but it is still there.
How do I remove this entry so that I can get back to my original backup?

try operator command DDIB to see the DIB. If there is a hung-up entry in there, use the ADADBS RESETDIB command to clear it.

Thanks Douglas. I am familiar with the DDIB and RESETDIB on the mainframe, but cannot find such a thing on unix. However, your response promted me to look around some more. I found the appropriate commands in the ADADBM utility - eg ADADBM db=xx display=ucb to see the internal ID and ADADBM db=xx reset=ucb,ident=yyyyy. There does not seem to be an equivalent reset command with the ADAOPR utility…

RESET=UCB is an ADADBM parameter, not an ADAOPR parameter.