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Database Forum / Informix Topics / September 2008Interview type Question
Hi, I am learning Informix, my PM asked me the following question, Please help me on this : You are a new employee at the company and the only Informix DBA. You were just informed by the management that one of the Informix DB Server is performing very badly for about a week now and that immediate analysis should be conducted. You are not familiar with the applications or the databases yet, but they ask you to find the problem as soon as possible. Please detail your plan of action, tools that you will use along the process, what would you check and how would you continue if you did not find any issue at the level or resource you are checking. Please explain things in a high level along with assumptions and recommendations. Please give me ur step-by-step level to proceed for the above scenario. Thanks in Advance. With Regards, Raja. > Hi, > [quoted text clipped - 12 lines] > Please explain things in a high level along with assumptions and > recommendations. Have you tried running UPDATE STATISTICS? > Hi, > [quoted text clipped - 19 lines] > With Regards, > Raja. Hello Raja, I find it best to go from the general to the specific. I would first run "system administrator" commands to see how busy the disk, CPU's and memory are. If your informix server is on a Unix operating system, then run ps -ef, vmstat 3 3, iostat 3 3, sar, etc. I would also check swapping (paging memory in and out to disk) which hurts performance. The second thing I would do is run informix commands like "onstat -g sql xxxx" where xxxx is the number you get from the previous command. Pay close attention to the WHERE clause. Can it use an index? If yes, then you may need to create one. Plus since you are new at this, I would advise you to run all the onstat commands. To get that list just enter "onstat --". When you have time, read the informix DBA manuals and/or after market books. They are all really quite good. It will be a LOT of reading but it will be worth it. Good luck! L.S. Hello Raja, I find it best to go from the general to the specific. I would first run "system administrator" commands to see how busy the disk, CPU's and memory are. If your informix server is on a Unix operating system, then run ps -ef, vmstat 3 3, iostat 3 3, sar, etc. I would also check swapping (paging memory in and out to disk) which hurts performance. The second thing I would do is run informix commands like "onstat -g sql xxxx" where xxxx is the number you get from the previous command. Pay close attention to the WHERE clause. Can it use an index? If yes, then you may need to create one. Plus since you are new at this, I would advise you to run all the onstat commands. To get that list just enter "onstat --". When you have time, read the informix DBA manuals and/or after market books. They are all really quite good. It will be a LOT of reading but it will be worth it. Good luck! L.S. > Hi, > [quoted text clipped - 19 lines] > With Regards, > Raja. Hello Raja, I find it best to go from the general to the specific. I would first run "system administrator" commands to see how busy the disk, CPU's and memory are. If your informix server is on a Unix operating system, then run ps -ef, vmstat 3 3, iostat 3 3, sar, etc. I would also check swapping (paging memory in and out to disk) which hurts performance. The second thing I would do is run informix commands like "onstat -g sql xxxx" where xxxx is the number you get from the previous command. Pay close attention to the WHERE clause. Can it use an index? If yes, then you may need to create one. Plus since you are new at this, I would advise you to run all the onstat commands. To get that list just enter "onstat --". When you have time, read the informix DBA manuals and/or after market books. They are all really quite good. It will be a LOT of reading but it will be worth it. Good luck! L.S. >> Hi, >> [quoted text clipped - 28 lines] > also check swapping (paging memory in and out to disk) which hurts > performance. Before I even did that, I'd ask myself - "If the system performance seemed to worsen within the past two weeks, then what changed within that same time frame?" ;-) > The second thing I would do is run informix commands like "onstat -g > sql xxxx" where xxxx is the number you get from the previous command. [quoted text clipped - 9 lines] > Good luck! > L.S. > > Hi, > [quoted text clipped - 42 lines] > Good luck! > L.S. The record's stuck... the record's stuck... :-) Actually I'm afraid that one shouldn't answer that question. Seems to me that this is a sample interview question so raja can get a job as an informix dba. > Hi, > [quoted text clipped - 19 lines] > With Regards, > Raja. The same question was asked on c.d.o. Are you doing double shifts?  SignatureFernando Nunes Portugal http://informix-technology.blogspot.com My email works... but I don't check it frequently... |
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