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Automated Linux VM build on ESX

How to automatically install RedHat like (Red Hat, Cent OS, Oracle Enterprise Linux) Linux system on ESX or VirtualBox servers ? There are at least two methods. I have seen VM cloning in lot of places using ESX (VSphere Center) or VirtualBox functionality. Cloning is fine but it required some intervention after clone will be finished (like host rename or IP address change). What if we want to install different releases of systems - well it is required to have a clone of every single release like RedHat 6.2, OEL 6.3 or OEL 6.4. It require a rework every time a new release is available on the market.

Recovering a standby over the network in 12c

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 had the standby shut down in my lab environment (intentionally) and created a few PDBs on my primary. For some reason I lost an archived redo log. This would of course not happen in a production environment, but my lab VM is limited when it comes to space and I may have moved my backup to a USB disk that I didn’t bring along.

Recovering a standby over the network in 12c

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 had the standby shut down in my lab environment (intentionally) and created a few PDBs on my primary. For some reason I lost an archived redo log. This would of course not happen in a production environment, but my lab VM is limited when it comes to space and I may have moved my backup to a USB disk that I didn’t bring along.

Interesting GNS anomaly in 12.1.0.1.2 RAC

I was encountering an interesting anomaly with my 12.1.0.1.2 RAC cluster based on Grid Naming System. I have written about the setup here.

Interesting GNS anomaly in 12.1.0.1.2 RAC

I was encountering an interesting anomaly with my 12.1.0.1.2 RAC cluster based on Grid Naming System. I have written about the setup here.

Linux strace doesn’t lie after all.

strace is a linux utility to profile system calls. Using strace you can see the system calls that a process executes, in order to investigate the inner working or performance. In my presentation about multiblock reads I put the text ‘strace lies’. This is NOT correct. My current understanding is that strace does show every system call made by an executable. So…why did I make that statement? (editorial note: this article dives into the inner working of Linux AIO)

Investigating the wait interface via gdb.

For some time now, I am using gdb to trace the inner working of the Oracle database. The reason for using gdb instead of systemtap or Oracle’s dtrace is the lack of user-level tracing with Linux. I am using this on Linux because most of my work is happening on Linux.

In order to see the same information with gdb on the system calls of Oracle as strace, there’s the Oracle debug info repository. This requires a bit of explanation. When strace is used on a process doing IO that Oracle executes asynchronous, the IO calls as seen with strace look something like this:

Runtime Load Balancing Advisory in RAC 12c-addendum

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 in for a given CON_ID.

During testing I noticed something interesting though. I queried gv$servicemetric but did not limit the result to the service I wanted to test with (FCFSRV). Here is the query against gv$servicemetric while the system was idle.

Runtime Load Balancing Advisory in RAC 12c-addendum

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 in for a given CON_ID.

During testing I noticed something interesting though. I queried gv$servicemetric but did not limit the result to the service I wanted to test with (FCFSRV). Here is the query against gv$servicemetric while the system was idle.