Hierarchical Blocking Session List

Hi, Today, I needed to list all blocking sessions hierarchically. As you know, all information about sessions (and blocking sessions) are in gv$session (or just v$session if you are using single instance) view. I wanted to see who is blocking who and blocker at the top. you can write simple connect by (or with clause)

Subquery Caching

Hi, I want to talk about very sweet performance “trick”. I love when I do something small and gain a lot 🙂 Today, I will demonstrate subquery caching in Oracle and try to explain how it works and it’s limitations. Probably, you are using some plsql functions in your select (or dml) statements. There is

Why should you use PLSQL_OPTIMIZE_LEVEL as 3

Hi, As you know PLSQL_OPTIMIZE_LEVEL parameter is used to optimize the codes while compiling them and it is really important. By default it’s value is 2 but you can increase it to 3 and you should, here is why. before begin, this is an extension for this post: http://mustafakalayci.me/2020/06/26/performance-gain-of-nocopy-parameters/ Very much thanks to Stephan Borsodi who

Enable Unified Audit on Linux and Windows

Hi, As you know, since 12c Oracle introduce Unified Auditing which has much more capabilities than standard auditing. Creating policies, audit conditions, top level auditing etc. By default Oracle uses “mixed” mode which allows you to run unified auditing commands and standard auditing. you can check if you are using unified auditing by default:

Direct Path Insert &/vs Conventional Insert

Hi there, I couldn’t write anything for a while. Those days were busy. So I would talk to about direct path insert and conventional insert. Many people think that they are using “direct path insert” when used sqlldr utility but they are not. it is easy to confused batch insert and direct path insert. of

Flashback Data Archive Problems!

Hi, if you don’t know about flashback data archive you can check this post first: http://mustafakalayci.me/2019/03/02/goodbye-log-triggers-welcome-flashback-data-archive/ I mentioned about flashback data archive (FDA) in that post and really flattered it. Well, maybe I shouldn’t! FDA is really fast dml tracking method but thanks to Peter Schlaeger, I noticed some potential problems and “some” solutions. Few

Oracle Table Compression Part1

Hi, I have been dealing with table compression a lot during my development period and I still do. I wanted to share some information about table information but I believe this will be a long explanation so I will write them in parts and this is part1. Table compression is a very useful feature of