Re: Data Dictionary Cache - DC_HISTOGRAM_DEFS ??

Are you running 7.3 ?

When you analyse in 7.3, entries are made in hist_head$ for the min and max value for each column of a table, even if you do not request histogram analysis.

When the CBO cuts in, it checks for relevant histogram data. Since you don't have any, the dc_ will always show 100% misses.

Note: In 7.3.2, if any of your tables are declared as parallel, then the CBO will cut in, even if your init.ora goal is RULE.

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Jonathan Lewis
ora_mail_at_jlcomp.demon.co.uk