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Foreign Keys and Library Cache Locks

In this post I would like to describe a behavior of Oracle Database that, at least for me, isn’t obvious at all. Actually, it’s something that I can’t explain why it works in that way.

Let’s start by setting the scene by describing the schema I’m using for the following tests. As you can see from the image, there are three tables: one table (PARENT) that is referenced by two other tables (CHILD1 and CHILD2). Schema used for the tests In my case every table is owned by a different schema (P, C1 and C2 respectively). But, the behavior I describe is independent from that fact (i.e. it works in the same way if all tables are owned by the same schema). If you are interested, here is the SQL*Plus script I used to create them.

Systematic Oracle Latch Contention troubleshooting

As an Oracle DBA, developer or performance analyst, you may have run into what is termed "latch contention" at various points. So what exactly is a "latch" and why do we have contention on this "latch". In this article, we will take an in-depth look at latches and how we determine and resolve such contention. Whether you are a newbie or an experienced old-timer, we hope this article will cast a little more light on this ill-understood subject.
Read the article here:

Oracle Latch Contention Troubleshooting

I wrote a latch contention troubleshooting article for IOUG Select journal last year (it was published earlier this year). I have uploaded this to tech.E2SN too, I recommend you to read it if you want to become systematic about latch contention troubleshooting:

I’m working on getting the commenting & feedback work at tech.E2SN site too, but for now you can comment here at this blog entry…