HI Peter:
Thanks for your answer. I have understand your answer. Thank you very much. ―――――――――――――――――――――――――― Best regards Timo Seven blog: http://zauc.wordpress.com #####请翻墙浏览，或者指定hosts到74.200.243.252####### UNIX System Admin 2010/3/23 Peter Zaitsev <p...@percona.com> > Hi, > > Lets see If I can help. > > Overly long queries (transactions >> in general) are bad for performance as a lot of unpurged versions >> accumulate. >> >> In this sentence, I don't know the meaning about 'unpureged version >> accumulate' >> > > When rows are updated new versions are created. They are later removed by > purge thread - only then no active transactions may need them. This is why > long open transactions are expensive. > > > >> >> >> And I don't how to understanding 'open transaction'? >> > > This is transaction which is started (opened) but not yet ended by commit > or rollback. > > > >> >> >> Required for logical level replication to work properly. >> >> What's the meaning about logical level replication? >> > > MySQL has statement level, also caused logical as well as row based > replication. statement level replication requires updates to be > serializable to work. > > >> >> >> Can give problems for portable applications if you port from MySQL-4.0 to >> later >> >> What's the meaning about this sentence? >> >> >> > This means you can run into the problems if you upgrade from MySQL 4.0 to > later version. Probably is not much relevant any more. > > > > -- > Peter Zaitsev, CEO, Percona Inc. > Tel: +1 888 401 3401 ext 501 Skype: peter_zaitsev > 24/7 Emergency Line +1 888 401 3401 ext 911 > > Percona Training Workshops > http://www.percona.com/training/ >
