Hi, Thank You for the answer, Does this mean that the frequency and range of journal memory flushes is determined by the O/S and the every-10-seconds synchronisation is an additional activity, carried out "just in case" ? What should I do if this regular synchronisation degrades performace of the system ? I changed the frequency to 10.000 seconds ( on my test environment, of course ) so that the system works much better. However, I'm not sure if it's safe for the data. Is this posible to switch off this sync completely and use only flushing by O/S ? Piotr W dniu środa, 28 stycznia 2015 16:42:24 UTC+1 użytkownik DanE napisał: > > The flush is a maximum period of time, not a constant. Most O/S will > flush in milliseconds depending on system load. Unless the transaction > load is huge, this is not normally something that needs to be altered. I > believe it really is more of a safety net thing that never really comes > into play. > > > > What is responsible for flushing is either the process updating the logset > or optionally a separate process running jlogsync. > > > > Dan Ell > > > > > *Dan Ell *Technical Support Engineer > > *jBASE *9245 Research Drive, Irvine, CA 92618 > 949-383-2429 > [email protected] <javascript:> > www.jbase.com > > *From:* [email protected] <javascript:> [mailto: > [email protected] <javascript:>] *On Behalf Of *My_jBase > *Sent:* Wednesday, January 28, 2015 8:03 AM > *To:* [email protected] <javascript:> > *Subject:* TIME BETWEEN LOG FILE SYNCS > > > > Hello, > > > > Would You like to explain me how jbase journal works ? > > The jbase manual says : > > > > When journaling is running the basic order of operations for updates is as > follows: > > • The database item is updated in memory > > *• The transaction log is updated in memory*. > > • The transaction log is flushed every 10 seconds by default. However this > time period can be configured via an option on the administration command, > jlogadmin. It is also possible to configure an independent process to > execute the jlogsync command, to ensure the transaction log is continuously > flushed from memory at the specified interval, thus alleviating the flush > procedure from all of the update processes. > > • The database updates are flushed to disk by the operating system. > > • The database update to disk and the log update to disk can be forced to > be an atomic operation. > > There is a feature which specifies the number of seconds between each > synchronization of the log set with the disk - jlogadmin -s nnn ; All > memory used by the log set is force flushed to disk. Should the system > crash, the maximum amount of possible data loss is limited to the updates > which occurred since the last log set synchronization. By default it is 10 > seconds. What will be if I change this to f.e. 10.000 seconds ? - does > that mean that I can lose informations from 10.000 seconds if my system > will crash ? > > In my opinion it's not true because I can observe modify time of logset > files during a test and they are constantly updated - not in every 10 or > 10.000 seconds > > So what is responsible for logsets synchronization ? > > > > Piotr > > > > -- > -- > IMPORTANT: T24/Globus posts are no longer accepted on this forum. > > To post, send email to [email protected] <javascript:> > To unsubscribe, send email to [email protected] <javascript:> > For more options, visit this group at > http://groups.google.com/group/jBASE?hl=en > > --- > You received this message because you are subscribed to the Google Groups > "jBASE" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected] <javascript:>. > For more options, visit https://groups.google.com/d/optout. >
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