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Simora: Alpha Testers Confirmed

It's been a while since I provided any public updates regarding Simora, our Oracle workload simulation product. It's finally time to unveil the status of Simora and our steps moving forwards. We have been working extensively on the Simora engine and infrastructure over the  last several months, with a view to transforming it into a […]

Simora: Alpha Testers Confirmed

It's been a while since I provided any public updates regarding Simora, our Oracle workload simulation product. It's finally time to unveil the status of Simora and our steps moving forwards. We have been working extensively on the Simora engine and infrastructure over the  last several months, with a view to transforming it into a […]

Systemtap revisited

Some time back, I investigated the options to do profiling of processes in Linux. One of the things I investigated was systemtap. After careful investigation I came to the conclusion that systemtap was not really useful for my investigations, because it only worked in kernelspace, only very limited in userspace. The limitation of working in userspace was that you had to define your own markers in the source code of the program you wanted to profile with systemtap and compile that. Since my investigations are mostly around Oracle products, which are closed source, this doesn’t help me at all.

Performance live discussion on twitter, 12pm PST Tue April 15

Confio software is hosting a live discussion on twitter tomorrow Tuesday April 15 at 12pm PST on the subject of Oracle performance.

I’ll be online answering performance questions and have invited many other friends to participate. Some friends who’ve said they’ll be there are

Participation and tracking of the discussion can accomplished by either posting with and  following along with the #datachat  hashtag.

Cache anomaly

Just a quick heads-up for anyone who likes to play around with the Keep and Recycle caches.

In 11g Oracle introduced the option for serial direct path reads for tablescans on tables that was sufficiently large – which meant more than the small_table_threshold – provided the table wasn’t already sufficient well cached.  (The rules mean that the choice of mechanism can appear to be a little random in the production environment for tables that are near the threshold size – but if you try testing by doing “alter system flush buffer_cache” you find that you always get direct path reads in testing.)

Cache anomaly

Just a quick heads-up for anyone who likes to play around with the Keep and Recycle caches.

In 11g Oracle introduced the option for serial direct path reads for tablescans on tables that was sufficiently large – which meant more than the small_table_threshold – provided the table wasn’t already sufficient well cached.  (The rules mean that the choice of mechanism can appear to be a little random in the production environment for tables that are near the threshold size – but if you try testing by doing “alter system flush buffer_cache” you find that you always get direct path reads in testing.)

New Version Of XPLAN_ASH Utility

A minor update 4.01 to the XPLAN_ASH utility is available for download.

As usual the latest version can be downloaded here.

These are the notes from the change log:

- More info for RAC Cross Instance Parallel Execution: Many sections now show a GLOBAL aggregate info in addition to instance-specific data

- The Parallel Execution Server Set detection and ASSUMED_DEGREE info now makes use of the undocumented PX_STEP_ID and PX_STEPS_ARG info (bit mask part of the PX_FLAGS column) on 11.2.0.2+

- Since version 4.0 added from 11.2.0.2 on the PX *MAX* DOP in the "SQL statement execution ASH Summary" based on the new PX_FLAGS column of ASH it makes sense to add a PX *MIN* DOP in the summary to see at one glance if different DOPs were used or not

IT Stockholm Syndrome

Shrugging

Random thoughts on a Friday afternoon…

We’ve all got problems. More to the point, every IT department or team has problems of some kind. It’s why we hire consultants, buy products, start long and arduous journeys into the great unknown depths of root cause analysis, and so on.

What fascinates me is the level at which we come to identify with our problems. When I’ve gone into an environment to deliver recommendations, the conversation usually goes something like this:

The Power of Nope