Hi Geetanjali, Well word of caution with this setting, it can block the whole server if the purge thread is delayed too much. Also look into other things like IO saturation or issues with disk as to why the purge thread is not able to keep up with the backlog. If IO is not the issue then there is a very old read view, which might be blocking the purge thread, so long running transactions not recommended.
We have seen situations where a bad disk had caused huge History_length. Cheers!!! Akshay On Tue, Sep 2, 2014 at 12:27 PM, geetanjali mehra < mailtogeetanj...@gmail.com> wrote: > Could you please put some more light on it? > > Best Regards, > Geetanjali Mehra > Senior Oracle and MySQL DBA Corporate Trainer and Database Security > Specialist > > > > On Thu, Aug 28, 2014 at 2:09 AM, shawn l.green <shawn.l.gr...@oracle.com> > wrote: > > > Hello Geetanjali, > > > > > > On 8/26/2014 1:16 AM, geetanjali mehra wrote: > > > >> I want to understand how to tune innodb_max_purge_lag > >> <http://dev.mysql.com/doc/refman/5.5/en/innodb- > >> parameters.html#sysvar_innodb_max_purge_lag> > >> > >> when history list length is high. > >> > >> > >> Could anyone explain me. > >> > >> > >> Best Regards, > >> Geetanjali Mehra > >> Senior Oracle and MySQL DBA Corporate Trainer and Database Security > >> Specialist > >> > >> > > This setting not related to the history value. It is there to help > control > > the gap between these two values of the InnoDB status report > > > > Trx id counter 0 290328385 > > Purge done for trx's n:o < 0 290315608 undo n:o < 0 17 > > > > What is the current transaction compared what is the oldest transaction > > that still has aged copies of data left in the data area of the > tablespace. > > The difference between those two values is the "purge backlog" > > > > Yours, > > -- > > Shawn Green > > MySQL Senior Principal Technical Support Engineer > > Oracle USA, Inc. - Hardware and Software, Engineered to Work Together. > > Office: Blountville, TN > > > > -- > > MySQL General Mailing List > > For list archives: http://lists.mysql.com/mysql > > To unsubscribe: http://lists.mysql.com/mysql > > > > >
