Sequences on Oracle databases are simple, but there are some basic truths about sequences which need to be understood if you are going to use them, especially on RAC:
- Sequences will have “holes” in them, even if you specify NOCACHE (e.g. if you rollback your transaction).
- Don’t specify NOCACHE. It doesn’t scale.
- Sequences will NOT necessarily be, erm, sequential for your transactions. That will depend upon the COMMIT order and if you are (more...)
With the INMEMORY clause you can specify 4 sub-clauses:
- The MEMCOMPRESS clause specifies whether and how compression is used
- The PRIORITY clause specifies the priority (“order”) in which the segments are loaded when the IMCS is populated
- The DISTRIBUTE clause specifies how data is distributed across RAC instances
- The DUPLICATE clause specifies whether and how data is duplicated across RAC instances
The aim of this post is not to describe these attribues in detail. Instead, (more...)
Thank you for attending my session RAC'fying Multitenant at Oracle Open World 2014. You can download the slide deck here
As always I would love to hear from you.
Thank you all those who attended my session Cache Fusion Demystified.
As I mentioned, it was impossible to fit in a demo within that compressed 45 minute timeline. I put the details of the demo
in a separate file with all the scripts and instructions that allows you to execute the demos at your own site.Download the slide deck
as well as the scripts. In addition I have also written a whitepaper
to explain (more...)
I have recently configured Active/Passive Failover cluster using Grid Infrastructure 12cR1 and wrote document on that subject. Now I plan to use this environment and convert "test12" database from Single-Instance to RAC database.
There are several ways to convert non-RAC database to RAC database:
- using Database Configuration Assistant (DBCA)
- Oracle Enterprise Manager
- rconfig command line utility
In this post I will describe how to perform conversion using rconfig utility
I noticed something for the first time tonight when I was playing around in the Enkitec lab – something that I have been doing wrong for a while. When working in the lab, I often rely on the crsctl command to shut down the entire cluster stack for me. It’s really easy to use “crsctl stop cluster -all” followed by “dcli -l root -g ~/dbs_group /u01/app/22.214.171.124/grid/bin/crsctl stop crs” to get everything down (more...)
This post is about exploring the mechanisms used by Oracle Clusterware 126.96.36.199 to restrict remote service registration, i.e. the 12c new feature "Restricting Service Registration for Oracle RAC Deployments"Why is this useful?
This improvement of 12c clusterware and listeners over the 11.2 version is useful mainly for security purposes, for example as a measure against TNS poisoning attacks (see also CVE-2012-1675
), and it is particularly relevant for (more...)
I had quite an interesting case recently where I had to build stretch cluster for a customer using Oracle GI 12.1 and placing quorum voting disk on NFS. There is a document at OTN regarding the stretch clusters and using NFS as a third location for voting disk but it has information for 11.2 only as of the moment. Assuming there is no difference in the NFS parameters I used the Linux parameters (more...)
Removing a service via srvctl has not historically resulted in the service being fully removed from the database and it would still be visible in DBA_SERVICES as show below in an 188.8.131.52 database:
Create the service:
$ srvctl add service -d orcl -s demo -r "ORCL1,ORCL2"
During my project work I had to tune the SOA dehydration store on more than one occasion. Through this posting I would like to share the tuning tips collected during these exercises. It is not a step-by-step guide, because with tuning there never is a 'one-size-fits-all' in my humble opinion, but I provide in general a guidance that you can use as a reference for your own situation. I will also refer to related Oracle (more...)
Original Post can be viewed at MGMTDB: Grid Infrastructure Management Repository
MGMTDB is new database instance which is used for storing Cluster Health Monitor (CHM) data. In 11g this was being stored in berkley database but starting Oracle database 12c it is configured as Oracle Database Instance. In 11g, .bdb files (more...)
Original Post can be viewed at Openfiler on Virtualbox and 12c Oracle Flex ASM
Last week Oracle released 12c database and Oracle blogosphere is bustling with lot of people posting details about new versions and setup. I too decided to take plunge and setup my own RAC cluster. I had (more...)
Original Post can be viewed at portmap: unrecognized service on RHEL6
Quick note for people using NFS for shared storage on RAC database. Till RHEL5 we had to ensure nfs,nfslock and portmap service has to be running. These services are required otherwise you will get following errors while mounting database (more...)
[I originally posted this over at the Pythian blog. If you're not following it, you should! Way more content, by far smarter people than lil ol' me.]
After reviewing my blog post about running EBS OVM templates in VirtualBox, two of my teammates suggested that I work on something with potentially broader appeal. Their basic message was, "This is really cool for us EBS nerds, but what about the Core DBAs?"
So how does "11gR2 RAC in an hour" sound? In this post, I'll demonstrate how to deploy the pre-built Oracle VM templates to create a two-node (more...)
This is just a post ot point out that ODA Patch 2.4 is out. ODA Patch 2.4 requires 2.2 or above to install.
A couple of Highlights of this release seem to be
- Enhanced odachk 2.16
- A trace file analyzer
- The ability to now use normal (more...)
Recently I was given three virtual machines running Oracle Enterprise Linux 5 and Oracle 11gR2 RAC on Oracle VM 2.2.1, copied straight from /OVS/running_pool/. I had to get these machines up and running at my lab environment, but I found hard to setup the network. I’ve spent half day in debugging without success, but finally found a workaround, which I’ll explain here.
Just a little technical notes – Oracle VM (xen) has three main setup configurations within /etc/xen/xend-config.sxp:
Bridge Networking – this configuration is configured by default and it’s simplest to configure. Using this type of networking (more...)
When instance fails in Oracle RAC, the services that were using this instance as a preferred instance are automatically relocated to instances marked as available for this service. But after the failed instance recovers and starts up again, the relocated services are not moved back and need manual srvctl relocate service command from administrator to move them back.
Here is a little Bash script to automate this process. Oracle Clusterware (Grid Infrastructure) can execute user callout scripts on FAN events, like INSTANCE up/down. Place this script under $GRID_HOME/racg/usrco/ and set the execute bits on the file. Then clusterware will execute (more...)
Tuning has always being good fun and something like a challenge for me.
From time to time we are being asked to find out why something did run slow while you are sleeping; answering this question is, in most cases, a challenge.
My batch did run slow last night, can you let us know why? Or why did this query run slow? Are questions we, as DBAs, have to answer from time to (more...)
I have extended the Undo usage scripts to include two additional indicators:
1) undo change vector size statistics
2) Used undo records/blocks
and support for RAC infrastructure, so you can spot the hungriest UNDO eaters for any given instance.
Then the script for Oracle 11g is as follows:
set pagesize 400
set linesize 140
col name for a25
col program for a50
col username for a12
col osuser for a12
SELECT a.inst_id, a.sid, c.username, c.osuser, c.program, b.name,
a.value, d.used_urec, d.used_ublk
FROM gv$sesstat a, v$statname (more...)