It´s been a while since my last post because i was busy doing some projects. One of these projects involved installing a rac cluster with ASM in normal redundancy mode. My experiences installing this configuration is covered in this article.
The customer requested the installation of an 2-node-rac cluster running a 10g Release 2 database. Storage was attached via fibre channel coming from two EMC AX25 storage systems directly attached to both nodes. The cluster was installed with 11.1.0.7.0 clusterware and 11.1.0.7.0 asm. The database to be run was 10.2.0.4.2. By using ASM and normal redundancy mode both storage arrays were mirrored against each other. Everything worked well – too well. So after installing the whole cluster and setting up the database instance we performed some tests:
The first test was to interrupt the connection (pull the cable!) between storage array A and node A. From my experiences with 11g R2 and asm in normal redundancy mode i expected to database to stay up and running. To my surprise the database on node A crashed. In addition to that i was unable to start the instance again. I cannot give the exact error message because the project ended and i am not allowed to disclose the messages. Among several ORA-00600 messages i also saw messages saying the database was unable to write to the control file and open the redo logs. That was strange because ASM already started to dropping the missing disks from the disk group. In addition dropping the missing disks was not that easy. After re-adding the disks back to the disk group i tried to delete one LUN from the operating system selectively thus keeping communication, links and so on intact. The result did not change: The database instance on the affected node crashed and i was unable to start the instance again. After searching at meta link which yielded nothing we decided to give 11.1.0.7.1 a try:
After installing and creating a 11.1.0.7.1 database and increasing disk group compatibility from 10.2 to 11.1 we tried again to interrupt the connection between one storage array and one node. This time the instance crashed with an I/O error and was terminated by the log writer but was restarted seconds after that fine - a great improvement over 10.2. After discussion the customer decided to go with 11.1.0.7.1 instead of 10.2.0.4.2 and we continued our tests which were completed successfully. These tests involved for instance interrupting the communication from one storage array to both nodes and re-establishing the connection again (after waiting 15 minutes).
My conclusion is: ASM in mirrored configuration can be used from 11g Release 1 onwards and gets well with 11g R2 (see my tests with 11g R2 and ASM in normal redundancy configuration). With 10g ASM should rely on external redundancy.
As always: Please comment! I´m looking forward from your experiences with ASM in normal or high redundancy configurations and 10g R2 or 11g R1 databases.
I found the following question in my blog statistics:
“can we change kernel parameter in linux when oracle is running”
The answer is: Yes, of course!
You can alter any kernel parameter as long as it don’t require a reboot. If you set any kernel parameter to a lower value than your running database requires there wont be any impact in time – but there might be problems when your database continues to run (e.g. unable to start new sessions, degraded performance).Once your database is shut down and you lowered for instance the SHMMAX parameter you wont be able to start the instance.
Therefore you should make sure to increase the values and check twice!
I developed this topic last year while taking the OCP course. The instructor told us about oracle authentication and because i was a little bit bored i played around with it. My goal was to use oracle external authentication to authenticate against a radius server which authenticates against an active directly (or any other LDAP server).
With this technology you can implement a centralized password and account management quite easily although users still have to be created in the database and they still have to be granted roles and permission to them in the database. Active Directory (i will use this term in the whole article…. as said instead of active directory use can use another other LDAP server as well) is solely used to:
- verify the users password
- check the account state and grant access only if the account is not locked
For using this authentication mechanism the “Oracle Advanced Security Option” is needed.
Read more…
Classic Metalink retired the last weekend. New flash-bashed Metalink currently faces a lot of problems (to be honest: it is at the moment [12th November 2009] completely unusable). Beside this major errors there are other problems: such as incredible high cpu demand (on my system flash player takes 100% CPU accessing metalink).
If you´re looking for a non-flash alternative there is an HTML metalink interface available. You can find it here: https://supporthtml.oracle.com. At themoment the HTML portal is extremely slow and unstable….. but for companies which do not allow flash to be installed at all the only solution.
As of today i successfully passed the exam to become an OCE. Next certifiecation i am working on is “Oracle Database 10g: Real Application Clusters Administrator Certified Expert”.
A few months ago i tested yet another syslog implementation: rsyslog. Among all other available syslog implementation such as syslog or syslog-ng rsyslog offers some nice features such as:
- database support
- Failover log destinations
- syslog over tcp
- fine grain output format control
- high precision timestamps
- filer on any message part
- compatible with syslog
- encryption support
So i took the oracle module for rsyslog and tried to get it working. A documentation did not relly exists so i wrote one which is part of the module now. Recently i took a look at rsyslogd again and did some test with rsyslog – especially how to store syslog messages and log oracle audit messages in a queryable way in an oracle database. My experiences will be covered in this article.
Disclaimer: All scripts, packages, procedures are released under the GPL. You can use them freely but on your own risk. However i would like you to send me the changes you made so i can perhaps improve the components.
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As of today (09th November 2009) Oracle 11g Release 2 is available for Solaris SPARC.
You can download it from OTN.
The release includes database, client and grid infrastructure (aka “clusterware” as well).
According to the release schedule Oracle 11g Release 2 for Solaris INTEL is most likely to be released next. Windows is scheduled for the second quarter in 2010. See my previous post for more information about possible release dates.
Recently i came across a project where they built their own cheap storage. The whole story is documented here and here.
A colleague of me and i saw this project and wondered if this kind of storage could be used for databases as well. So we analyzed the design and noticed some problems from our point of view:
- data access only via HTTP
- they used the JFS file system which is not widely used
- generally hard disks are hot-swappable; but not used due to fear of problems
- optimized for space rather than for speed
- relatively “weak” power supply
So we tried to improve the layout with the following constraints:
- approx. 10.000 Euro (approx. 15.000 US-Dollar) in total
- Storage accessible via multiple protocols:
- NFS
- iSCSI
- NFS
- CIFS
- if possible SAN
- Reliable
- Optimized for speed rather than capacity (remember: we talked about databases)
- Hot-Swapable Harddisks
This is part I of our journey towards building a storage system ourself. Part II is here and Part III here.
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Beneath the battle of the operating systems (Windows vs.UNIX) there one argumentation after deciding for running oracle on Linux: The choice of the file system and the “correct” partition layout.
This article will sum up what file system are certified for running oracle on Linux (and other platforms as well) and will especially discuss the available file systems on Linux. My opinion regarding an optimal partition layout is written here.
Recommendations regarding the partition layout can be found in an older post here.
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Starting with Oracle 11g Oracle added several compression algorithms to compress data. They can be used for compressing tables, LOBs , compressed data pump exports or even RMAN backups. Unfortunately for some compression algorithms you need to purchase the “Advanced Compression Option”. The following table lists the available RMAN compression options, the most likely compression algorithm being used and states if an additional license is required:
| RMAN Compression Type | Compression Algorithm used | Adv. Compression License required? | Backup set size | CPU Load |
| BASIC | BZIP2 (100k record size?) | No | small | medium to high |
| NONE | none | No | largest; approx. db size | extremely small |
| | | | |
| LOW | LZO | YES | somewhat smaller than using NONE | low |
| MEDIUM | ZLIB | YES | medium | medium |
| HIGH | BZIP2 (900k record size?) | YES | smallest | highest |
This article is intended to take a look at the different compression methods available in Oracle 11g and to compare them.
