As an interesting aside, my database group at DEC was part of storage
engineering on the basis that Rdb/ELN was a prototype for a future DEC
database machine. The group manager was not the least bit pleased to hear
that we were doing data compression since, after all, he was in the business
of selling disks. I eventually convinced him that the real reason from
compression was for performance by decreasing the size of disk transfers
rather than reducing the amount of disk space used.

It wasn't the group manager's only dubious call. He initially turned Ann
down for a job because he decided that she wouldn't be able to get along
with me.

On Tue, Sep 27, 2011 at 11:24 AM, Ann Harrison <aharrison@...>wrote:

> **
>
>
> >
> >
> > A starting point:
> >
> >
> http://www.dba-oracle.com/oracle11g/sf_Oracle_11g_Data_Compression_Tips_for_the_DBA.html
>
> Wow! Just got into the history of compression and was stunned t learn that
> DB2 invented record level compression as early as 2006. "Standing on each
> other's feet", indeed.
>
> OK, here's my summary.
>
> Record level compression. We do it, InterBase did it in 1985, Rdb/ELN did
> it in 1982. The algorithm is primitive, but fast. Jim's got another
> algorithm that compresses 40% more which was described on this list a
> couple
> years ago. Snappy may be another choice, but may depend on having larger
> and more consistent sample than a typical record.
>
> Page level compression. Oracle does it, InnoDB does it. It would appear to
> make random access harder. Certainly for a disk system where you need to
> read and write fixed size blocks, compressing pages to odd lengths seems
> like an odd choice. Questions: how do you find a compressed page on disk?
> How do you prevent fragmentation when you need to write back a page that
> has grown or shrunk?
>
> Table level compression works only for systems that store tables
> contiguously.
>
> Cheers,
>
> Ann
>
> >
>
> [Non-text portions of this message have been removed]
>
>
>


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