November 2015

For all those attended my session at Northeast Oracle User Group at Babson College in Wellesley, MA. Have you ever wondered how Cache Fusion knows where to get the block from? Or, how block locks vary from row locks? Or you are confused about the meaning and purpose of various Global Cache Service (GCS), Global Resource Directory (GRD) and Global Enqueue Service (GES). The session was meant to explain how all these actually work under the covers with live demos.

It’s been over a decade since I first heard Tom Kyte talking about Project Marvel, which eventually became Application Express (APEX). Since then I’ve “used” just about every version of APEX. I use the term “used” very loosely, because I typically use APEX for a few days to get a job done, then never touch it again for months. By the time I come back, I pretty much have to start the learning process from the beginning again.

Here’s a little gem in 12c that arrived in my email a few days ago: a query where the result depends on the SQL*Plus arraysize!

The email had a short description, and a script to create a small data set that would demonstrate the problem. I’m not going to show you the query, or the result set, but here’s a sample of the output from an SQL*Plus session after creating the data. This is, by the way, on a “single-user” system – there is no way that some other session is changing the data – especially after the opening “set transaction”:

If the inputs to the CBO change, the plan can change. For example, changes to bind variables can cause the plan to change when it is hard parsed. Therefore one should never be surprised when plans change.(read more)