Re: Informix vs. Sybase vs. Oracle vs. (gasp) MS SQL Server

In article <frLQBCADmlVzEwN4_at_smooth1.demon.co.uk>, David Williams <djw_at_smooth1.demon.co.uk> writes:
> In article <5j39eg$2sj_at_mew.corp.sgi.com>, Pablo Sanchez
> <pablo_at_mew.corp.sgi.com> writes
> >
> >In article <0v8awLAcPRVzEwpS_at_smooth1.demon.co.uk>, David Williams
> ><djw_at_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?

> 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 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."

> 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?

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