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04-20-2008, 06:40 AM
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 Virtual Memory Question for IDS 7.31 on Windows Hi all, I have a question regarding the virtual memory portion of informix shared memory. What is the comparison between the size of the resident memory compared to the size of the virtual memory? i.e, if the resident portion is 700MB, what should the virtual portion be? This for a db/CI server running informix 7.31.TD1X2 on Windows 2000 SP4 with 4GB physical memory and 10GB pagefile. Resident memory is at 175000 buffers (700MB), currently virtual portion is 400MB. I am seeing that the virtual portion has been extending up to 6 times a month constantly and am looking for recommended values to reduce this extending. Thanks and regards Stefan ************************************************** ******************** This email and any files transmitted with it are confidential and intended solely for the use of the individual or entity to whom they are addressed. If you have received this email in error please notify the sender and delete the material from any computer. You can visit Nylex at http://www.nylex.com.au ************************************************** ******************** sending to informix-list      |
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04-20-2008, 06:40 AM
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| Re: Virtual Memory Question for IDS 7.31 on Windows Stefan.Gabriel@nylex.com.au wrote: > Hi all, > > I have a question regarding the virtual memory portion of informix shared > memory. What is the comparison between the size of the resident memory > compared to the size of the virtual memory? i.e, if the resident portion is > 700MB, what should the virtual portion be? This depends much on what is going on. I know installations with 3 or 4 configurations. Fx one configuration for data loading - here almost all memory is allocated to BUFFERS (resident shared memory), another configuration for index build allocates most of the memory for virtual shared memory and a third configuration with almost even split between resident and virtual for "normal" production. > > This for a db/CI server running informix 7.31.TD1X2 on Windows 2000 SP4 > with 4GB physical memory and 10GB pagefile. Resident memory is at 175000 > buffers (700MB), currently virtual portion is 400MB. I am seeing that the > virtual portion has been extending up to 6 times a month constantly and am > looking for recommended values to reduce this extending. With 4GB memory Windows2K splits the memory into 2 GB system memory and 2GB user memory. You can add the '/3GB' option to the boot line in the boot.ini file. With this option memory is split into 1 GB system memory and 3GB user memory. This will usually reduce the os paging. When the virtual shared memory is growing you should look at the application. Sometimes an index can reduce the need for vsm, sometimes you must rewrite sql statements. If it's a particular app (fx a monthly report) that makes IDS allocate a lot virtual shared memory, you can often free the memory afterwards with the 'onmode -F' command. |
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04-20-2008, 06:40 AM
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| Re: Virtual Memory Question for IDS 7.31 on Windows On Tue, 14 Sep 2004 18:17:30 -0400, Stefan.Gabriel wrote: > Hi all, > > I have a question regarding the virtual memory portion of informix shared > memory. What is the comparison between the size of the resident memory > compared to the size of the virtual memory? i.e, if the resident portion is > 700MB, what should the virtual portion be? There's no relationship between the two. Virtual memory is tied to query complexity and so it application dependent more than anything else. > This for a db/CI server running informix 7.31.TD1X2 on Windows 2000 SP4 with > 4GB physical memory and 10GB pagefile. Resident memory is at 175000 buffers > (700MB), currently virtual portion is 400MB. I am seeing that the virtual > portion has been extending up to 6 times a month constantly and am looking > for recommended values to reduce this extending. Then beyond taking Claus's advice and making sure that queries are sane, you need to increase the SHMVIRTSIZE by 6 times SHMADD and possibly increase the size of SHMADD going forward. Each dynamic add stops processing by all CPU VPs, so they can integrate the new data structures, for from one to 30 seconds depending on many factors, so fewer dynamic virtual memory adds is preferred. Art S. Kagel |
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