Qian Qiao schrieb: > On 10/30/05, Alexander Skwar <[EMAIL PROTECTED]> wrote:
>> Well, but how does it work in a DBMS? Does a transaction >> log there save you from a 'DELETE FROM table; COMMIT;'? >> I mean, I suppose you could see - thanks to the transaction >> log - that a 'DELETE FROM table;' was done, who did it >> and when it was done. >> > > It does, technically. Does it? How? So the log contains what rows are in the table? How large is the log? If I have a look at the archived redo logs of some Oracle DBs, I see that they tend to be gigantic - if you also count what's been written away and archived on backup tapes. But those logs are a bit different than FS journals. The DBMS logs contain everything that's been done. Every row that's added (INSERT) or every change (UPDATE). > The way DBMS maintains table consistancy opon > failure is to re-play transactions logged. Yes. This would mean, that the system would notice that "DELETE FROM table;" has not yet been (successfully/completely) run, wouldn't it? > These logs are not the logs > that appear in /var/log, they are maintained internally by the DBMS. Sure. Alexander Skwar -- [email protected] mailing list
