fuzzy checkpoint
Manel Falco i Aige asked what 'fuzzy checkpoint' in online.log means after upgrading from 7.30 to 9.21. Neil Truby and Naresh Chainani explained that IDS 9.2x does not flush all modified pages at a checkpoint, shortening checkpoint time during heavy DML. Art S. Kagel added that it should affect cache rates only slightly, and that 7.31 already partly implements it. Answered.
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What does "fuzzy checkpoint" means from online.log file ? always is "fuzzy" ? I have recently upgraded from 7.30 to 9.21 and it seems it records more info now Regards, Manel Falcó
You need to get hold of a manual or perhaps go on a conversion course. Basically IDS 9.20 has introduced "fuzzy checkpointing" where not all modified pages are written back to disk during a checkpoint, thus enabling better cacheing rates. Manel Falc' i Aige <manel@semic.es> wrote in message news:39ec9194.38195411@news.bcn.ttd.net... > What does "fuzzy checkpoint" means from online.log file ? always is > "fuzzy" ? > I have recently upgraded from 7.30 to 9.21 and it seems it records > more info now > > Regards, > Manel Falc' >
A very concise description for fuzzy checkpoint : Normally during a checkpoint, all modified buffers are flushed to the disk. Now, if there is a lot of DML activity in the server, the time for a checpoint increases as more pages are to be flushed to the disk and during this checkpoint period, user sessions cannot connect to the server. To reduce the checkpoint period 9.2x introduced the concept of fuzzy checkpoints wherein not all the modified pages will be flushed to the disk. U can obtain more details in manuals post-9.20x, I guess. The manuals are online at http://www.informix.com/answers. Naresh "Manel Falcó i Aige" wrote: > > What does "fuzzy checkpoint" means from online.log file ? always is > "fuzzy" ? > I have recently upgraded from 7.30 to 9.21 and it seems it records > more info now > > Regards, > Manel Falcó -- *===========================*=====================================* | | Informix Software Inc. | | | Informix Center, 10th Floor, | | Naresh Chainani | 315 SW Fifth Avenue, | | E-mail : | Portland, Oregon 97204, USA | | naresh@informix.com | Tel : (O) 1-503-525 7548 | | | (R) 1-503-228 9612 | | | Fax : (O) 1-503-721 2369 | *===========================*=====================================*
Actually, fuzzy checkpointing should not directly affect cache percentages and the indirect effect should be slight. Just because 7.xx flushed most of the dirty pages (7.31 actually partially implements fuzzy checkpointing without fanfare) does not mean that the pages are not available in the cache any longer to be rewritten. The flushed buffers are just moved from the dirty queue to the head of the clean queue where while they are now available to be overwritten unless the cache is way too small they will just as likely be rewritten as overwritten since they will be MRU pages in the clean LRU queue. Art S. Kagel Neil Truby wrote: > > You need to get hold of a manual or perhaps go on a conversion course. > Basically IDS 9.20 has introduced "fuzzy checkpointing" where not all > modified pages are written back to disk during a checkpoint, thus enabling > better cacheing rates. > > Manel Falcó i Aige <manel@semic.es> wrote in message > news:39ec9194.38195411@news.bcn.ttd.net... > > What does "fuzzy checkpoint" means from online.log file ? always is > > "fuzzy" ? > > I have recently upgraded from 7.30 to 9.21 and it seems it records > > more info now > > > > Regards, > > Manel Falcó > >