Re: ESQL/C transaction logging - outside a transaction?

>From: jharris@westpac.com.au (Jason Harris) >Date: Wed, 20 Aug 1997 20:56:41 GMT >X-Informix-List-Id: <news.41847> > >Dear All, > >My 0.02c worth. > >1. If the database is mode ANSI then any statement starts an implicit > transaction, ... Near enough correct that I'm not going to quibble... ROLLBACK WORK and COMMIT WORK could be said to leave the database outside a transaction, but since almost any other statement (other than CLOSE DATABASE) starts a new transaction, it is a bit difficult to spot the difference. > ... if just normal logging then only data modifying statements start a > transaction. Not really, and the only reason I'm responding to this message is because this is not completely accurate. In a plain logged database, the only statement which starts a transaction is BEGIN WORK. In an OnLine database with logging (MODE ANSI or not), every statement is atomic - either it succeeds completely, or it fails completely and it is as if the statement never executed at all. This is similar to a transaction, but is distinct from a transaction, because the same property applies whether the statement is executed inside an explicit user-activated transaction or not. I think it is achieved internally by using a savepoint to mark an intermediate point in the transaction which the engine can roll back to if the statement fails. I think that unlogged OnLine database have the same property of atomic statements, but I'm feeling rusty enough not to be definitive on that point. And SE has different properties again... >2. Correlated subqueries [...] > >On 20 Aug 1997 01:24:05 GMT, satriguy@aol.com (SaTriGuy) wrote: > >>>Can anyone tell me why >>>transactions are being created when we never even begin a transaction to >>>start with and does anyone know whether there's a way to turn this stuff >>>off for particular apps and/or ESQL/C functions? Thanks. >> >>If the database is a logging database, then there is an implicit >>transaction arround every command so that individual transactions can be >>rolled back. Also, disk allocation/deallocations are always logged, even >>with unlogged databases. Finally, any dml statements (i.e. create table, >>etc) will be logged. >> >>Probably the best thing to do to figure out what is being logged is to >>dump the log files via onlog (tblog). Yours, Jonathan Leffler (johnl@informix.com) #include <disclaimer.h> PS: Warning I do not reply to messages with anti-spam in the return path.