There is a db2 server : DB2 OS/390 8.1.0,

procedure, that simply inserts data into table ins_prib_k('PR','657803','A','3030030',5,1100,'20' ,'1',2111,'З717818','864300','242005','100001','13 134131','05','1222',' ','ОАО СинтеЗ')

One of the parameters contains cyrillic letters('ОАО СинтеЗ').

In case procedure is called from .net WebService using DB2Command object, cyrillic letters get into db in form like : 'О�О СинтеЗ'

If i call the same procedure from IBM DB2 client, or from other client (for example Quest Central for DB2), everything is fine.



what is the problem ?

This is clearly an UTF-8 issue: read in groups of two, except for the space, the above are the 9 two-byte UTF-8 encodings for the Cyrillic text 'ОАО СинтеЗ' to be inserted.
So in this case apparently the server received the correct bytes, but did not interpret them as UTF-8 as it should have done.
Verify the communication settings between your client (.net) and the server, and make sure it is set to UTF-8 (unicode).
(Sorry, I don't know anything about dotnet, so I cannot be of any more help...)

I tried to convert procedure call to different encodings. No luck.

Tried to find DB2Command or DB2Connection properties, related to encoding; Still no luck.