Re: Informix and isolation modes

Hi, The only difference between committed read and dirty read is that committed read will only allow reading of rows that have been committed to the database where dirty read will. Neither place locks with normal cursors. UPDATE CURSORS will place locks even if you use dirty or committed read. You didn't mention the logging mode of your database or the definition of the transactions you are using that are leading to this problem. I suspect that it is here that you will find your problem. Also, what lock mode are you using for the tables you are selecting from (row or page)? In short, if you have transactions in your application all locks aquired during the span of the transaction remain until the end of the transaction. Since you have an isolation level of committed read the only locks placed on rows already in your database tables will be: 1) Rows modified through an UPDATE statement i.e. UPDATE table_x SET (...) WHERE col_x = @##$; 2) The current row of an UPDATE CURSOR. i.e. FETCH update_cursor; 3) Rows modified through an UPDATE WHERE CURRENT OF i.e. UPDATE table_x SET (...) WHERE CURRENT OF curs_x; -Bill > > We have an application that runs with the isolation set to committed read. > Sometimes the application locks up when we enter dbaccess and do selects > against a table the application uses. This is very infrequent but can > occur even when we set our isolation mode to dirty read while in dbaccess. > > Are their any Informix Guru's who can restore :-) my faith in Informix by > helping with the following questions? > > 1) Have you ever heard of anything like this before? > 2) Do readers affect writers in Informix??? (yuck) > 3) What are we doing wrong? > > 4) If the answers to 1,2,3 are yes, yes, and nothing then is SQL Server > any good or is it just a toy? :-) > > thanks for the help! > Mike Serafino > > -------------------==== Posted via Deja News ====----------------------- > http://www.dejanews.com/ Search, Read, Post to Usenet > -- Bill Ennis Voice: 312-474-7516 SSA Fax: 312-474-7460 500 W. Madison email: ennis@ssax.com ennis@accesschicago.net