Experimenting with the ZFSSA’s snapshot capability using the simulator

Recently I have been asked how the Copy-on-Write cloning works on the ZFS Storage Appliance. More specifically, the question was about the “master” copy: did it have to be static or could it be rolled forward? What better than a test to work out how it works. Unfortunately I don’t have an actual system available to me at home so I had to revert to the simulator, hoping that it represents the real appliance accurately.

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Trouble with multiple SCAN listeners in 12c Release 1

Prompted by comments made by readers about my posts describing how to add a second SCAN in 12c Release 1 and problems regarding the listener_networks parameter I thought it was time to revisit the situation. I’m still running Oracle Linux 7.1/UEK3 (although that should not matter) but upgraded to 12.1.0.2.5. This is the release that is reportedly showing the odd behaviour. I don’t recall my exact version when I wrote (more...)

TABLE ACCESS INMEMORY FULL – but there may be more

While preparing to teach a class this week I have had the time to look into the In Memory (cost) option a bit closer. I noticed a few interesting things along the way and would like to share one of these here.

Background

One of the questions I was asking myself was:

“What happens if I scan segments that are within the IM area, and some are not?”

I was primarily thinking of joins in (more...)

Little things worth knowing: automatic generation of extended statistics in 12c Part II

In my last post I demonstrated an example how to use a PL/SQL package to monitor a workload in order to identify correlated columns. Such columns are good candidates for the creation of extended statistics since the optimiser does not assume that information stored in different columns may be related. Before starting my tests I invoked DBMS_STATS.SEED_COL_USAGE, which in turn increased Oracle’s attention level trying to find correlated columns. Eventually these have been identified (more...)

Little things worth knowing: automatic generation of extended statistics in 12c

When you are migrating to Oracle 12c I hope you might this post useful. I came across this feature when researching what’s new with Oracle 12c (and yes I still find lots of new ones I haven’t noticed before). This one is a bit hidden away in section 2.2.4.3 Automatic Column Group Detection of the 12c New Features Guide. And it’s a lot more complex than I first thought! In this first post (more...)

Example of Full Transportable Export to create a 12c PDB

The Cool Stuff

Oracle has introduced a new way of transporting data from one platform to another in 12c. The new feature is called “Full Transportable Export”. This enhancement works from 11.2.0.3 and later and is a great way to move data, as it allows for an easy-to-use combination of Export Data Pump and Transportable Tablespaces. The documentation specifically praises it as a means to move from an 11g Release 2 database into (more...)

CloneDB in Oracle 12.1.0.2

I personally really like CloneDB, a way to thin-clone an Oracle database over NFS. This can be quite interesting, and I wanted to update my blog for 12.1.0.2.3 (April PSU). Tim Hall has a good example for 11.2.0.2 and later, and I covered cloneDB it in the Consolidation Book in some detail as well.

My setup is as follows:

  • server3 (Oracle Linux 7.1) uses Oracle Restart and has (more...)

Fixing a problem with the ASM spfile preventing RAC 12c from starting

This is a little note to myself on how to fix a corrupt spfile in clustered ASM. I hope you find it useful, too.

Let’s assume you made a change to the ASM (server) parameter file that causes an issue. You are most likely to notice this once CRS is restarted but parts of the stack fail to come up. If “crsctl check crs” mentions any component not started you can try to find out (more...)

Little things worth knowing: Data Guard Broker Setup changes in 12c

One of the problems I have seen when deploying Data Guard for systems such as RAC One Node and policy managed databases was the static listener configuration you needed in 11.2. This has changed with 12c for the better if you are using Grid Infrastructure.

http://docs.oracle.com/database/121/DGBKR/install.htm

In the section about static listener registration a little addendum can be found (thanks to Patrick Hurley/@phurley for pointing this out to me!):

“A (more...)

JSON support in Exadata 12.1.2.1.0 and later

Some time ago Oracle announced that RDBMS 12.1.0.2 has built-in support for JSON processing. A little later it was also mentioned that you have support for JSON in the Exadata storage servers for offloading. This is probably a lot more exciting to users of JSON than it is to me as I’m not a developer. However, whenever an announcement such as the one I’m referring to is made I would like to (more...)