BUFFERS parameter - lost?

Hi, I am sorry to bother you but I am completely lost with parameter "BUFFERS". I thought that BUFFERS represent maximum number of buffers (units!) and that my buffer space is BUFFERS * buffer size (2048 bytes) So if I need to hold 20 % of my 100 mega application data (= 20 Mb)in the buffer space, how many buffers do I need? I thought I would set parameter BUFFERS to 10 000 because 10 000 * 2048 = 20 480 000 bytes = 20,48 MB. Am I completely wrong??? I red Informix manual and their say about BUFFERS parameter as follows: Parameter: BUFFERS Number of Units: bytes Maximum value: 768 kilobytes Do BUFFERS parameter specify some kind of space in kilobytes and not a number of 2048 byte buffers? And how do I understand the maximum value for the parameter? This may be the most stupid question you have ever heard, but I would greatly appreciate your help. I do not anybody here to ask from. Best Regards, Kati / Finland Sent via Deja.com http://www.deja.com/ Before you buy.

heikkka4@my-deja.com wrote: > > Hi, > > I am sorry to bother you but I am completely lost with parameter > "BUFFERS". I thought that BUFFERS represent maximum number of buffers > (units!) and that my buffer space is BUFFERS * buffer size (2048 bytes) > The buffer size is also the page size for your OS (as shown by onstat -b). In the case of my HP system, it's 2048. > So if I need to hold 20 % of my 100 mega application data (= 20 Mb)in > the buffer space, how many buffers do I need? > I thought I would set parameter BUFFERS to 10 000 because > 10 000 * 2048 = 20 480 000 bytes = 20,48 MB. > Am I completely wrong??? > No, you're right. > I red Informix manual and their say about BUFFERS parameter as > follows: > > Parameter: BUFFERS > Number of Units: bytes > Maximum value: 768 kilobytes > It seems a bit confusing. Further along in the manual, it shows that the buffer space is BUFFERS * system page size. The BUFFERS variable defines the number of buffers that Informix will allocate upon startup. > Do BUFFERS parameter specify some kind of space in kilobytes > and not a number of 2048 byte buffers? And how do I understand > the maximum value for the parameter? > No, it specifies the number of BUFFERS to allocate upon startup. See above. > This may be the most stupid question you have ever heard, but > I would greatly appreciate your help. I do not anybody here > to ask from. > No such thing as a stupid question. After spending three years in classroom (teaching), I've learned that the only stupid question is the unasked question. John Carlson Informix DBA WHSmith USA > Best Regards, > > Kati / Finland > > Sent via Deja.com http://www.deja.com/ > Before you buy.

It looks like Carlson answered most of your questions, but there's one thing I can add. You're misreading the 768K limit for buffers. The limit is not 768 KiloBYTES as you thought (i.e., NOT 768 thousand BYTES). It's 768 thousand BUFFERS, at 2K (or whatever your page size is) each! Actually, 768 * 1024 buffers, or 786,432 buffers. I don't think you'll be needing that many! :) Their wording in the manual is kind of bad, but this explanation should help it make sense. Hope this helps, - Tom <heikkka4@my-deja.com> wrote in message news:820png$hk7$1@nnrp1.deja.com... > Hi, > > I am sorry to bother you but I am completely lost with parameter > "BUFFERS". I thought that BUFFERS represent maximum number of buffers > (units!) and that my buffer space is BUFFERS * buffer size (2048 bytes) > > So if I need to hold 20 % of my 100 mega application data (= 20 Mb)in > the buffer space, how many buffers do I need? > I thought I would set parameter BUFFERS to 10 000 because > 10 000 * 2048 = 20 480 000 bytes = 20,48 MB. > Am I completely wrong??? > > I red Informix manual and their say about BUFFERS parameter as > follows: > > Parameter: BUFFERS > Number of Units: bytes > Maximum value: 768 kilobytes > > Do BUFFERS parameter specify some kind of space in kilobytes > and not a number of 2048 byte buffers? And how do I understand > the maximum value for the parameter? > > This may be the most stupid question you have ever heard, but > I would greatly appreciate your help. I do not anybody here > to ask from. > > Best Regards, > > Kati / Finland > > > > > > > > > > > > > > > > > > > > Sent via Deja.com http://www.deja.com/ > Before you buy.

heikkka4@my-deja.com wrote: > Hi, > > I am sorry to bother you but I am completely lost with parameter > "BUFFERS". I thought that BUFFERS represent maximum number of buffers > (units!) and that my buffer space is BUFFERS * buffer size (2048 bytes) > > So if I need to hold 20 % of my 100 mega application data (= 20 Mb)in > the buffer space, how many buffers do I need? > I thought I would set parameter BUFFERS to 10 000 because > 10 000 * 2048 = 20 480 000 bytes = 20,48 MB. > Am I completely wrong??? > > I red Informix manual and their say about BUFFERS parameter as > follows: > > Parameter: BUFFERS > Number of Units: bytes > Maximum value: 768 kilobytes > > Do BUFFERS parameter specify some kind of space in kilobytes > and not a number of 2048 byte buffers? And how do I understand > the maximum value for the parameter? > > This may be the most stupid question you have ever heard, but > I would greatly appreciate your help. I do not anybody here > to ask from. > > Best Regards, > > Kati / Finland > > Sent via Deja.com http://www.deja.com/ > Before you buy. As I understand it, a buffer is a memory page. On my SUN machine, a memory page is 2048 bytes (or 2 Kb). So, using your example, if your page size is 2Kb and 20% of your available memory is 20Mb, then your number of buffers should be 20Mb / 2Kb In other words - memory divided by size of one buffer. HTH, Avi. -- /\\ \\ /| Avi Abrami, Analyst/Programmer, Telegate Ltd. /__\\ \\ / | 7 Haplada Street, Or-Yehuda, ISRAEL / \\ \\/ | Phone:+972-3-5388717 Fax:+972-3-5335877 eMail:avia@telegate.co.il

Many thanks to all of you for aswering. You where a great help. I understand it now. Best Recards Katja Sent via Deja.com http://www.deja.com/ Before you buy.