Re: Informix vs. Sybase vs. Oracle vs. (gasp) MS SQL Server
In article <5j5tv5$14s@mew.corp.sgi.com>, Pablo Sanchez <news_reader@mew.corp.sgi.com> writes > >In article <frLQBCADmlVzEwN4@smooth1.demon.co.uk>, David Williams ><djw@smooth1.demon.co.uk> writes: >> In article <5j39eg$2sj@mew.corp.sgi.com>, Pablo Sanchez >> <pablo@mew.corp.sgi.com> writes >> > >> >In article <0v8awLAcPRVzEwpS@smooth1.demon.co.uk>, David Williams >> ><djw@smooth1.demon.co.uk> writes: >> >A big ++++ for Sybase that Informix currently does not have is >> >that the buffer cache can be partitioned and tables/indexes... can >> >be found to portions of the cache. Rather than treating the cache >> >as an unknown, the DBA is allowed to micro manage it. They can >> >change the wash section, I/O pool size (for reading/writing).... >> >quite nifty. >> >> Surely this will reduce performance for unbound cache entries? > >Absolutely! > >Of course typical DBA action would be (atomically): > > 1) create the named partition (Sybase lingo) > 2) create the I/O pools within the named partition > 3) bind one or more objects to the pool. > 4) run a bench and monitoring tool to ensure that it's being > used. > >A neat idea (well, okay, IMHO) is that you can have a configuration >for "normal" operation and a configuration for "crunching" >operation. Cool eh? > Cool. >> I would have thought that binding objects into the cache only >> helps in limits cicumstances?? > >Most applications benefit from it because minimally you can create a >named partition for your database log(s) and bind them to it. The >high turnover rate of dirty buffers is now restricted to a small area >in memory. Neat eh? And of course, if you have a mixed workload on But Online uses seperate buffers for logging - 3 logical log buffers and 2 physical log buffers. These are separate from the normal buffers which buffer database pages rather than log pages. >your RDBMS, you can bind frequently scanned tables to a named cache >so that they don't flush out the working set established in the >"default cache." If you have frequently scannign tables you will be using a DSS application hence should be using PDQ and LIGHT SCANS (scans which do NOT utilise the normal buffers hence do not affect the working set in normal BUFFERS. > >> Informix has a logical log buffer - up to one logical log can >> be buffered at a time - I'm not sure what the I/O size is that >> is used for writing logical log buffers to disk... > >This is *my* weakness because we didn't go into this in class like I >thought we would (no fault of the instructor... he had a lot to >cover) and next thing ya know, the class was over! :-(... I really >want to learn more about how connections send their transactions to >the logical log and how the physical log relates to the logical log. > >Any reading you recommend? and/or websites with info? Online Admin Guide Version 7.1 Volume 1 Section v Logging and Log Administration. Especially Pages 22-23 to 22-24 (overall logging description) Chapter 20 (What is Logging) Chapter 24 (Physical Logging) and Chapter 26 (What is Fast Recovery) >-- >Pablo Sanchez | wk: 415.933.3812| pg: 800.930.5635 -or- pablo_p@pager.sgi.com >--------------+-----------------+-------------------------------------------- >pablo@sgi.com ... when mailing me, place "not spam" in the Subject -- David Williams