Index cluster with one table

[vsevolod afanassiev]

A vendor provided scripts for table creation in a new database.
Some tables get created in index clusters, however each cluster
contains only one table.
Does it make sense? I thought that idea behind clusters was to combine
two or more tables
to make joins faster.

By the way SYS schema also has clusters, and two of them (this is
10.2.0.5) have only one table:
Cluster HISTGRM$ table C_OBJ#INITCOL#
Cluster SMON_SCN_TIME table SMON_SCN_TO_TIME

[Jonathan Lewis]

"vsevolod afanassiev" <vsevolod....@gmail.com> wrote in message
news:75f08b8f-7a5d-419e...@t2g2000pbg.googlegroups.com...

|A vendor provided scripts for table creation in a new database.
| Some tables get created in index clusters, however each cluster
| contains only one table.
| Does it make sense? I thought that idea behind clusters was to combine
| two or more tables to make joins faster.
|

Yes, it can make sense.

You might want to cluster together rows from the same table even though
they appear at very different times. Clustering for joins was just one
reason for clustering. Note that Oracle uses many single table (hash)
clusters in its TPC-C records.

The same time of thinking applies to Index Organized Tables - data arrives
in one pattern, but is stored in another pattern for faster (group)
retrieval.


--
Regards

Jonathan Lewis
http://jonathanlewis.wordpress.com
Oracle Core (Apress 2011)
http://www.apress.com/9781430239543