I have two databases on NT.Both version is :8.1.5.449

while working with drda(i`ve made nicknames in database A to use database B`s tables),i got error QL30090N reason code:18

The help says something about two_phase_commit and set it to Y.

how to do it?

have a look at spm (syncpoint management) in admin guide : implement
I don't think this error has todo with this :
- do you use update/.. when being in a luw on nickname with update/.. on local object ? otherwise include a commit to close the luw.

spm is only used if really updates are needed in the same luw being on objects that have to be in synch..
Hope this will help
Best Regards, Guy Przytula

i am still in trouble