I regularly read threads on the oracle-l mailing list, and occasionally feel very tempted to reply to one. Just recently I saw one that I liked a lot. It is specifically about using an Oracle Database Appliance (ODA) as a Disaster Recovery (DR) solution for an Exadata system. The Exadata configuration was not specified, I assume it was a smaller (eighth rack/quarter rack) configuration.
There were lots of arguments pro and against that Exadata->ODA architecture, (more...)
This post is related to 12c and an active database duplication for a standby I did in my lab environment. I’d say although I first encountered it on 12c there is a chance you run into a similar situation with earlier releases too.
I would normally use ASM for all my databases to make my life easier but this time I had to be mindful of the available memory on the laptop-which at 8 GB-is (more...)
Another one of the cool but underrated features in 12c is the possibility to recover a physical standby over the network with one line in RMAN.
Why do you need to perform this activity? Assume someone really clever created a segment “nologging” and the database was not in force logging mode. This operation cannot be replicated by redo apply on the standby, and you are bound to have a problem. Or, in my case, I (more...)
I was encountering an interesting anomaly with my 126.96.36.199.2 RAC cluster based on Grid Naming System. I have written about the setup here.
No need to get back to the post-instead let me give you some background if you are not familiar with the Grid Naming System in RAC. Most RAC installations use a Domain Name Server (DNS) to resolve names to IP addresses. In the case of GNS the name (more...)
A reader asked an interesting question yesterday with regards to the previous post on the subject: where did you get your service metrics from when you queried v$servicemetric-PDB or CDB$ROOT?
I queried the PDB, but this morning repeated the test to make sure the results are consistent, and they are. This is definitely something you’d hope for: you should not have different results in the same v$-view depending on the container you execute your query (more...)
This is a follow-up on yesterday’s post about services in the new 12c database architecture. After having worked out everything I needed to know about TAF and RAC 12c in CDBs I wanted to check how FCF works with PDBs today. While investigating I found out that the Runtime Load Balancing Advisory does not seem to work as expected. To double-check, I ran the same test against a 12c non-CDB and noticed that the RTLB (more...)
In preparation of the OUGN Spring Seminar and to finally fulfill at least a part of my promise from July I was getting ready to research RAC, PDBs and services for my demos. It turned out to become a lot more interesting than I first assumed.
RAC and Multi-Tenancy
So the first attempt to really look at how this works has started with my 2 node cluster where I created a RAC database: RAC12C, administrator (more...)
I had the great fortune to have had many of my abstract accepted for upcoming conferences and other public appearances, the first ones for this year are these:
The first conference I’ll be attending is in Dublin, for OUG Ireland 2014 on March 11.I’m going to help out with RAC Attack and also present about Technologies for Developing Highly Available Applications in RAC 12c at 14:50 for about 45 minutes. What can you (more...)
I have come across this phenomenon a couple of times now so I thought it was worth writing up.
Consider a scenario where you get an alert because your standby database has an apply lag. The alert is generated by OEM and when you log in and check-it has indeed an apply lag. Even worse, the apply lag increases with every refresh of the page! I tagged this as an 11.2 problem but it’s (more...)
I have been asked to investigate another interesting problem worth writing about. It’s worth mentioning here because it deals with a problem I believed to have long since been solved: tablespace fragmentation. However, in this case it was a locally managed tablespace (LMT) with Automatic Segment Space Management (ASSM) enabled. It should be difficult to have fragmentation on one of these, but as you will see it is not impossible.
So the story started innocently (more...)