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Oracle Data Dictionary Pocket Reference David C Kreines
Published by O'Reilly and Associates
144 pages
£ 8.95
Published: 3rd June 2003
reviewed by Mike Smith
   in the December 2003 issue (pdf), (html)

What is to say about a pocket reference? This one has 129 tiny pages, plus an index. Quite often I think a reference as surplus to requirements, as google is often quicker for finding that snippet of information you require. However I'm sure they have their place for flicking through to discover new things. Its always a challenge to know (i.e. be aware of) what you don't know.

This reference is for Oracle 9i Release 2 - so good for a few more weeks! The 10g database is being released in November or December, I think. But don't let that put you off - and to be fair, it was published in April apparently.

I started working with Oracle way back ... Version 6, and the data dictionary structure (which had a major revamp at that time) hasn't changed significantly since - though of course there have been continual enhancements release after release. The book has a brief overview of the structure, and explanation of nomenclature, then we're into the meat.

Where I think the book shines is the categorisation of the information. I mentioned the index. Its good to have a list of objects, but this still takes 10 pages (each with 60 or more items). The problem with an index, as always, is that its alphabetic and if you're looking for, say, that table which has some information on columns its a problem. (ie there are several tables, and they are dotted about all over the index). You'd be better off at the SQLPlus prompt with a

select table_name from dba_tables where table_name like '%COL%'

clause, or a show command or similar. Oh, and the V listing is a bit bloated (that's an in joke for you DBAs - V$, you know.)

Anyway, I digress; Back to the point. The various views and what-have-you are put into categories, so the book isn't just an alphabetic list of data dictionary objects. There are sections on tables, indexes, jobs, security - and the newer features like replication and partitioning. Then there's OPS (yuk!) and RAC (yum!) too. Not all in that order actually - the sections themselves are placed in an alphabetic fashion to show no favouritism. (There are many more categories, I just haven't listed them.)

The book is split into two major sections - almost exactly down the middle. I've talked about the first half so far, except for my little (and very poor) joke above. The second half covers this area - the dynamic views. For those non-DBAers (though goodness knows why you're reading this, you brave souls) the dynamic views are the ones which commence with a 'v$'. As if there isn't enough confusion over what v$ views are (you may or may not know that most are actually views of the x$ tables), they then go and introduce gv$ views in Oracle 8 too.

So this latter half has page after page of v$ views.

I usually only seem to do a select * from v$database -- to see where I am (... oh, okay sometimes I look at locks when there's something funny going on, or latches to pretend I know what I'm doing with performance tuning. Hold on, there's another review on that subject somewhere!)

After my dismissiveness at the beginning or this article, I actually quite like this little guide. Its only a listing of data dictionary objects and their structure. But its always when I'm half way though a complex select statement that the mind goes blank -- ``Is it extent_name or segment_name in dba_extents ?" So now I have the option of picking up my Oracle Data Dictionary Pocket Reference and flicking through to page 55 to have a look. (Instead, that is, of the 50ms switch to another window to do a desc dba_extents and back again!) And I may notice on page 54 that the dba_data_files column for the auto extension flag is autoextensible, not autoextendable. That would be an easy mistake to make, I'm sure you'll agree !

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