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Min/Max

One of my most-repeated observations about trouble-shooting Oracle is that things break when you start combining features. Here’s an example that demonstrates the point.

It’s possible to create “descending” indexes – or indexes with descending columns, as I prefer to call them, and there’s a special “min/max range scan” optimizer operation for a particular kind of index usage – demonstrated in the following code fragment (running under 11.2.0.4, and reporting the rowsource execution statistics):

Min/Max

One of my most-repeated observations about trouble-shooting Oracle is that things break when you start combining features. Here’s an example that demonstrates the point.

It’s possible to create “descending” indexes – or indexes with descending columns, as I prefer to call them, and there’s a special “min/max range scan” optimizer operation for a particular kind of index usage – demonstrated in the following code fragment (running under 11.2.0.4, and reporting the rowsource execution statistics):

ASH Analytics- Activity Focused on Resource Consumption, Part II

This is the second post on ASH Analytics Detail.   You can find the first post here.

ASH Analytics- Activity Focused on SQL Data, Part I

I have a request to hit on some EM performance blog posts, so we’re going to start with breaking down some of the ASH Analytics areas.  ASH Analytics is not your grandfather’s “Top Activity” and I recommend everyone begin to embrace it as it is the the future of performance activity in the Enterprise Manager.  The idea that we will be able to pull directly from ASH and AWR to present our performance dat

IOUG Collaborate 2014 and EM12c Odyssey

Collaborate is coming up fast and this year is going to be a great conference for all involved.  I’ll have a number of sessions, both for those attending in person and those taking advantage of the virtual content.

RLS bug

RLS – row level security, aka VPD (virtual private database) or FGAC (fine grained access control) has a critical bug in 11g. The bug is unpublished, but gets mentioned in various other documents, so can be identified as: Bug: 7828323 “SYS_CONTEXTS RETURNS WRONG VALUE WITH SHARED_CONTEXT_SENSITIVE”

The title tells you nearly everything you need to know – if you’ve declared a security policy as context_sensitive or shared_context_sensitive then a change to the context ought to result in the associated predicate function being called to generate a new security predicate the next time the policy becomes relevant. Thanks to bug 7828323 this doesn’t always happen – so queries can return the wrong set of results.

RLS bug

RLS – row level security, aka VPD (virtual private database) or FGAC (fine grained access control) has a critical bug in 11g. The bug is unpublished, but gets mentioned in various other documents, so can be identified as: Bug: 7828323 “SYS_CONTEXTS RETURNS WRONG VALUE WITH SHARED_CONTEXT_SENSITIVE”

The title tells you nearly everything you need to know – if you’ve declared a security policy as context_sensitive or shared_context_sensitive then a change to the context ought to result in the associated predicate function being called to generate a new security predicate the next time the policy becomes relevant. Thanks to bug 7828323 this doesn’t always happen – so queries can return the wrong set of results.

Effective Indexing Webinar

Thanks to everyone for attending today's Effective Indexing webinar sponsored by IOUG with Embarcadero. For attendees, IOUG will likely send out a link to the recording and PDF of the presentation, but I also wanted to post it here.

Presentation PDF
Webinar recording

Oracle Scene Magazine Article

While I was in OUG Ireland I was given a copy of the latest Oracle Scene Magazine, which includes a little column about my Public Speaking Tips. You can see the write-up here.

Oracle Scene are always on the lookout for contributors. If you have something you think they might be interested in, go to the Article Submissions page.

Cheers

Tim…

Temporary Segments

A question came up on oracle-l recently about identifying which temporary segment in v$tempseg_usage is associated with which global temporary table. Here’s my answer:

v$tempseg_usage is a synonym for v$sort_usage – which is the view that I still tend to think of first.