The Blog from the DBA Classroom

By: Joel Goodman

Archive for January, 2009

DBA Seminars in UK and Ireland

Posted by Joel Goodman on 30/01/2009

I have updated my Seminars page with some interestting seminars in both London and Dublin. You may see this here.

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How does Oracle Certification Help find the Answers

Posted by Joel Goodman on 29/01/2009

I have created a page where I will discuss how Oracle Certification has helped me  “Understand the Questions”  and “Find the Answers” in the classroom.

If you teach Oracle DBA skills to anyone as a trainer, team leader  or even 1 to 1 as a mentor have  look here.

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Seminars for DBAs

Posted by Joel Goodman on 29/01/2009

I have created a new page where I will be listing information relevant for DBAs with limited time to spend in the classroom due to their work commitments. If you like the seminar format and prefer short, one or two day events then feel free to visit Seminars for DBAs.

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ASM Storage Possibilities

Posted by Joel Goodman on 22/01/2009

While delivering an Exadata Presentation to the UNIX SIG of the UKOUG  on Tuesday, I asked the audience of about 90 people how many used ASM and about 40% replied that they did.  ASM is very popular for RAC installations and increasingly used for Single Instance Oracle environments.

Most of the DBAs at the SIG used external volume managers serving logical volumes on a Storage Area Network and this is true of customers attending courses with me as well.

However it is not necessarily known that there are four possible solutions for ASM Disks so here is a summary of the possibilities:

1. External LUNs served by a Volume Manager – This is the most common solution and allows the use of “EXTERNAL REDUNDANCY” whereby the mirroring is done by the volume manager. This also provides for multi-pathing for High Availability in the storage network. ASMLIB may be used for this configuration on LINUX for persistant naming if UDEV is not already implemented. Many installations use Fibre Channel but iSCSI is possible as well. The “asm_diskstring” parameter specifies a list of one or more strings usually with wildcards, of the devices.

2. Local LUNs or Local Volumes – Local disks may be used by ASM in one of several ways. The disks may have 1 or more partitions, and these may be used as the ASM Disks.  Alternatively Local LUNs may be creates using local physical volumes, volume groups and logical volumes. This solution is good for sandbox solutions for education when no storage network is available or for smaller configurations when there is no storage network. RAC on Standard Edition requires ASM but a small to medium business may not have a storage network and could opt for this solution.  Note that ASMLIB may be used in this configuration as well but that no multi-pathing is available. Also no “External Redundancy” would be used here. The “asm_diskstring” parameter specifies a list of one or more strings usually with wildcards, of the devices.

3. Zero Padded Files on a NAS Filer – This is the least known solution but is used by some. A filer shares a file system rather than serving volumes so the Network Attached Storage file system must be created on the filer and accessed by the Oracle Database node using NFS. The “mount” command is used or an entry placed in /etc/fstab. To use this for ASM Disks, each “Disk” is actually a large file created on the NAS file system and then padded with zeroes using the “dd” command. The “asm_diskstring” parameter specifies a list of one or more strings usually with wildcards, of the path to the NAS files. Note that ASMLIB is NOT needed or used for this configuration.

4. Grid Disks on Exadata Cells – If Exadata is used, then the ASM Disks ar the so called “Grid Disks” configured in the Exadata Cell Servers. Exadata automatically implements Fail Groups providing redundancy. Note that ASMLIB is NOT used for Exadata and that the “asm_diskstring” parameter is set to an Exadata specific wildcard string of “o/<cell_ip_address>*/<griddisk_name>* ” allowing the discovery of the grid disks on all cell servers whose IP addesses match the wild card in the second part of the string and whose grid disk name mathces wild card in the third part of the string.

As a final point – a single ASM instance may access ASM Disks using a combination of two or more of these technologies. This could be done for example during a phased migration, or because the same or different databases using the same ASM instance use different storage tiers which are based on different storage solutions.

Posted in Oracle, User Group Presentations | Tagged: , , , | 10 Comments »

Speaking of Exadata….

Posted by Joel Goodman on 16/01/2009

I will be presenting an Oracle University Mini-lesson about the new Oracle Exadata feature at the UKOUG UNIX Special Interest Group meeting on 20/01/2009 from 14:30 to 15:30.

This will be of interest to Storage Administrators, Database Administrators and Data Warehouse installations in particular.  I look forward to seeing the UNIX SIG members on the day.

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Interested in Star Transformation Queries??

Posted by Joel Goodman on 15/01/2009

Oracle Data Warehouses often perform complex n-way joins with aggregating functions such as SUM , COUNT and AVG. Star Transformation is a type of rewrite technique for optimising such queries and exploits the power of bitmap indexes. To learn more about this feature please read the article I wrote for the Oracle University EMEA Newsletter.

>> Your Transformation is in the Stars

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Inside the DBA Classroom 1

Posted by Joel Goodman on 14/01/2009

I am often asked about my teaching goals when delivering courses or seminars to DBAs and what helps to make a successful class. There are several elements to a good presentation to any audience but I wish to share my strategy for  teaching technology.

1. Add Value – There is a balance to be struck between teaching what one knows and teaching a course. If a trainer “reads from the notes” then this adds no value to what a delegate could get from reading the book alone. But if one spends one or more days ignoring the notes entirely then delegates may have difficulty writing all the useful information provided by the trainer.  My goal is to “Add value” within the context of the structure of the course or seminar. That means being familiar with the material in such a way as to weave the extra detail into the story whilst sticking roughly to the plot of the course. Ideally delegates should be able to write the extra details and additional concepts but still find the course notes a useful structure and reference.

2. Obtain Collateral Knowledge and Skill – When teaching any course or seminar, questions arise that are not directly related to the course content. A delegate on a RAC course for example may work at a company that uses Oracle Streams and ask about Streams itself or Streams in relation to RAC. This situation is quite common and requires trainers to know many other “tangential” areas of technology to answer these questions or if not then at least to understand what is being asked.

3. Know the System – Knowing the technology requires hands on for practical knowledge in additon to the theoretical knowledge from the book. An ideal course is a mixture of theory and practice based on real knowledge and experience.  This is easier now than ever because of the availabilitu of virtualisation products making it easy to create one’s own sandbox in which to to play around.

4. Raise the Bar – Courses have degrees of difficulty but in all cases I try to raise the bar higher to push people harder. My view is simple; if an abstract bar exists to measure the level at which a course is pitched and is set at level 6 out of 10, then noone will get higher than 6 to get 100% attainment of the original target level of the bar. If the hypothetcal bar is set to 9 then some may not attain 9 but in striving to reach it they may get more than 6 so that average level may be higher than 6 even if 100% of the desired level is not attained.

Whilst these four elements of training have helped me in the classroom, I would recommend them for anyone involved in any form of teaching, mentoring, or knowledge transfer to colleagues.

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Articles and Presentations

Posted by Joel Goodman on 14/01/2009

I have posted recent articles and user group presentations on the Articles and Presentations page. Have a look and enjoy them. I hope they are of use.

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