Re: PCTFREE on indexes

From: Roderick Manalac <rmanalac_at_oracle.com>
Date: 22 Oct 1994 02:01:05 GMT
Message-ID: <389rp1$84g_at_dcsun4.us.oracle.com>


extel_at_world.std.com (Chris eastland) writes:
|> mdconnor_at_wheel.ucdavis.edu (Matt Connors) writes:
|>
|> >extel_at_world.std.com (Chris eastland) says:
|> >>
|> >>This is for a table with zero rows at creation with primary key index.
|> >>Will it do any good to set at 99% when there are no rows present? Not
|> >>an option to create indexes after dataload.
|> >>
|> >>Also, is there a better way to actually look at the data in the tablespace
|> >>(how it's laid out) than to use variously inventive cat or od (Unix)?
|> >>
|> >>chris
|> >>
|> >If I understand your question correctly, you are considering setting
|> >the pctfree parm for a primary key index at 99%. This will leave 99%
|> >of the block free for updates to the index (not inserts). Since a primary
|> >key index, by definition, will be on "not null" columns, pctfree could be
|> >as low as 0%. Hope this helps...
|>
|> Mmmm, ok. I guess I got from the manual that inserts like to have room
|> between a lower and a higher key to avoid chaining.
|>
|> chris

See page 8-33 of the Oracle7 Server Administrators Guide for how PCTFREE is used in the context of indexes. It is different than tables.

As far as the original question goes, PCTFREE would pretty much be ignored since the table would be empty.

No good answer for how to look at how data is laid out. Looking at rowid's would help show how tables are laid out. No straightforward way to look at indexes. Some of the statistics in DBA_INDEXES after an ANALYZE INDEX might help there.

Roderick Manalac
Oracle Corporation Received on Sat Oct 22 1994 - 03:01:05 CET

Original text of this message