Here is an interesting optimizer case where updated statistics and histograms cannot solve the performance problem. This might be an uncommon case, but it happened for one of my clients and this post is the result of some research on this.
One of my customers is a software company and they use Oracle database for their product. One of the things we need to do when they certify an Oracle version is to create silent installation scripts. These scripts are for Windows and used for demo and testing environments. I did that for 11.2 and for 12.1 and now it’s 12.2’s turn.
This post is following a question I found on LinkedIn. A DBA pasted a strange test case in 220.127.116.11 and I managed to reproduce it in 18.104.22.168 (non-multitenant) and 12.2 (multitenant). But that’s not where the story ends, I wanted to understand what’s going on, so I did some research about it and the result is this post.
A few months ago we hit an Oracle bug related to streams replication crash after creating an index (bug 21320182). There is a patch so we installed the patch in test and it seemed to solve the problem, but we never patched the production.
Today we hit this issue in production after creating an index we needed. It’s important to say that we wanted to patch the prod a while ago, but we didn’t get approval for maintenance window.
This week I worked on a messy patch. I have a RAC environment with 22.214.171.124 and an old PSU and all kind of one-off patches and I wanted to install the latest PSU (180417). It sounds simple, but it’s not so simple. The thing is that I have 4 database running from the same ORACLE_HOME, all of them are RAC, while some of them are stand-alone, some are primary for standby located on a different RAC and some are standby for a primary located on a different RAC. And the problem with that is that you cannot install a PSU on the primary first, either together or patch the standby first.
In our first BCOUG Tech Day conference, I presented my session “Look Inside the Locking Mechanism”. I presented this topics before a few times and prepared a few demos to show different locking scenarios.
During the BCOUG Tech Day I did the same, while the only difference was that for the demo I used Oracle 12.2 PDB (I think in previous times I always used 11.2). During one of the demos I noticed something strange.
Over the years I ran into all kind of weird and wonderful backup and restore scenarios. This case has challenged me for a while now and I finally had the chance to check it properly and figure out what’s going on. So here is the story.