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Interview type Question

Posted in 2008

Summary

Not a bug report but a request for help answering an interview-style question: a newcomer asked how to diagnose an Informix server that has been performing badly for a week, with no knowledge of the applications or databases. Replies suggested working from general to specific — check OS-level load with ps, vmstat, iostat, sar and look for paging/swapping, then use onstat commands (e.g. onstat -g sql <sid>, onstat -- for the list) to examine running SQL and whether WHERE clauses can use indexes; others suggested running UPDATE STATISTICS and, first of all, asking what changed in the last two weeks. One poster objected that the question shouldn't be answered since it was an interview test. No single resolution is recorded.

Auto-generated by DrWatson from the posts below — may be imperfect; read the full thread.

Topics: Server Administration

raja — — source: Usenet: comp.databases.informix

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.

↪ replying to raja
Neil Truby — — source: Usenet: comp.databases.informix

"raja" <dextersunil@gmail.com> wrote in message news:0d58fa44-2384-42ff-82ec-856e728bbfb1@m44g2000hsc.googlegroups.com... > 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. Have you tried running UPDATE STATISTICS?

↪ replying to raja
LIGHT SCANS — — source: Usenet: comp.databases.informix

On Sep 24, 9:48 am, raja <dextersu...@gmail.com> wrote: > 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. 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.

↪ replying to raja
LIGHT SCANS — — source: Usenet: comp.databases.informix

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.

↪ replying to raja
LIGHT SCANS — — source: Usenet: comp.databases.informix

On Sep 24, 9:48 am, raja <dextersu...@gmail.com> wrote: > 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. 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.

↪ replying to LIGHT SCANS
Madison Pruet — — source: Usenet: comp.databases.informix

LIGHT SCANS wrote: > On Sep 24, 9:48 am, raja <dextersu...@gmail.com> wrote: >> 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. > > 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. 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. > 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.

↪ replying to LIGHT SCANS
Ian Michael Gumby — — source: Usenet: comp.databases.informix

On Sep 24, 1:56 pm, LIGHT SCANS <light_sc...@yahoo.com> wrote: > On Sep 24, 9:48 am, raja <dextersu...@gmail.com> wrote: > > > > > 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. > > 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. 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.

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