About

Welcome to my blog! I hope that you will find interesting and useful things on this site. Let me start by telling you a bit about me so you can get an idea of where I am coming from. I read my first computer book at age 12. It was about the BASIC programming language. By age 16 I was doing computer work in the summer between school years. I majored in Computer Science at Harvard and Brown between 1983 and 1989. Then I started my full-time work on the IBM mainframe in 1989. I started working with Oracle database software around 1994 with Oracle 7.0.16 on SCO Unix supporting PeopleSoft HR and Financials 5.

I have done a variety of Oracle DBA tasks but I especially enjoy the challenge of Oracle database performance tuning. So, this blog has a lot of performance tuning content. But, this site also reflects the tasks that I am working on and the things that I am exploring. So, there are posts that are not performance tuning or even Oracle database. Yet, I think that “Bobby Durrett’s DBA Blog” is a reasonable title since I have spent so much time as a DBA. Performance tuning continues to interest me so I’ve kept that as a focus.

I have to include a warning here for anyone who decides to use the information on this blog. Please double-check anything you read here in other places. Also, if you plan to change a production database be sure to test your change on another system. You have to test things yourself. Don’t just take my word for it! 🙂

– Bobby

p.s. Feel free to interact with me by commenting on blog posts or contact me directly at bobby@bobbydurrettdba.com.  I am not selling any product or service so don’t worry – I won’t harass you with sales calls or email spam if you reach out to me.

p.p.s.  These two sites aggregate this blog:

http://orana.info/

http://www.orafaq.com/aggregator

Misc:

LinkedIn: My profile

Twitter: @bobbydurrettdba

GitHub: My URL

Oracle certifications: Oracle 7, 9, 10, 11, and 12. Here is a picture of me with my fun Oracle Certified Professional shirt that I bought after passing the 12c OCP test:

shirt

4 Responses to About

  1. Jeferson Bezerra says:

    Hi Bobby, I am Jeferson Bezerra, I work in Brazil as a Oracle DBA, I’m learning about Oracle performance tuning…

  2. Laurel says:

    Hi Bobby! Nice site with good info. Can you point me to right direction ?
    10g database 6G sga, 19G memory on server
    0.sql using HASH joins with full scans.
    1.Exactly same sqlplan /planhashvalue yesterday and today .
    Queried from cache and awr report to compare
    2. stats the same / the counts of rows practicaly the same (compared)
    3. But today its using Temporary tablespace for hash joins
    and last 1 hour
    4. Exported profile from working instance -> sql using -> still the same issue sorting on temp tablespace
    5. Noticed some minor paging on server
    5. altered policy to manual and gave lot of hash_area_size -> same

    What i am missing here ? 🙂
    Any hints ?
    Thank you!
    Br.Laurel

    • Bobby says:

      I’m not sure. One thing I have seen is that the plan does not always include all of the details of what the database does. So, forcing the profile or having the same plan hash value does not guarantee the same behavior as in the past in all aspects. I read some things in Jonathan Lewis’ book about hash joins and when they spill to disk versus using PGA. It might be a good resource for you or his web site. You say there is sorting to the temp tablespace. The hash join doesn’t do sorting I don’t think. I think it just puts part of the hash table on disk when needed. Maybe you need to manually bump up sort area size if you are trying to manage the PGA manually, but that’s just a guess.

      If you could do select count(*) queries on the two sides of the hash join it might tell you how many rows are really part of the join although you may have done that already.

      Those are some ideas. Hard to know if this is helpful without digging into it myself.

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