dbi services Blog
Welcome to the dbi services Blog! This IT blog focuses on database, middleware, and OS technologies such as Oracle, Microsoft SQL Server & SharePoint, EMC Documentum, MySQL, PostgreSQL, Sybase, Unix/Linux, etc. The dbi services blog represents the view of our consultants, not necessarily that of dbi services. Feel free to comment on our blog postings.
I had the opportunity to attend Paul Randal’s session on advanced data recovery techniques at the Pass Summit. During this session one attendee asked Paul if a page that has just been corrupted can remain in the buffer pool extension (BPE). As you probably know, BPE only deals with clean pages. Paul hesitated a lot and asked us to test and this is exactly what I will do in the blog post.
When you have sessions blocked on locks, you probably have all information about the waiters (they call you and anyway their waiting session is visible in v$session our ASH). But you usually need to get enough information that help to identify the blocker.
I'm quickly checking the planning for DOAG these 3 days and here is the list of sessions I would like to attend.
There are still a lot of interesting ones even if my choice is limited by the language (I would like to understand German but I'm limited so sessions in English). And I've still some concurrency issues to solve because I cannot be at two places at the same time.
SQL plan Directives have been introduced in 12c. If you have scripts that check their states (and I have that as I prefer to monitor closely the features that are new) you probably have seen a difference when going from 22.214.171.124 - the first release of 12c and the only one avilable yet in Standard Edition - and 126.96.36.199 - the first patchest. I'll explain here what are the SQL Plan Directive states and how they changed.
In one of my last blog, named: "Oracle Audit Vault and Database Firewall (AVDF) 12.1 - installation on VirtualBox" I explained how to install AVDF on VirtualBox. Since some of you asked for a blog on "How to configure AVDF", I decided to write this posting on AVDF post-installation configuration. This one only concerns the post-installation phase, a third blog will be dedicated to practical cases concerning the configuration of Database Firewall Policies.
What is the most important part in an execution plan? It's probably the predicate section. It helps to see implicit conversions. It helps to understand why an index is used or not. Or to see additional predicates coming from constraints. When you get an execution plan from shared pool, the dbms_xplan.display_cursor() shows the predicates. But when you retrieve a plan from the past, dbms_xplan.display_awr() does not show them.
I've blogged about multitenant internals at the time when 188.8.131.52 was just released. Something has changed in 184.108.40.206 and blogging about it was in my todo list for a long time. Now the occasion to do it has been triggered by a question on Oracle Forums about CDB_DATA_FILES not showing PDB$SEED datafiles because there is an important change we must be aware of.
People often ask me if I use the SQL Tuning Advisor. The answer is no, at least not through the end of it. But don't take me wrong. SQL Tuning Advisor is a really nice feature. If you like the CBO then you must love the Tuning Advisor, because it is just the CBO with more time to optimize, and more ways to optimize. The fact is that when a customer calls me, they expect a bit more than running an advisor and implement the result. I'm there to fix the root cause, not just workaround some missing stats. And this is why I use it very rarely.