Re: RESIDENT and BUFFERPOOL
David E. Grove wrote: >>On Solaris the 4MB page size is used for any segment made resident, no >>matter how many there are. > > Since page size is now settable in IDS 10, does the above have any > implication on specifying a BUFFERPOOL page size? I'm no sure whether you understand how buffer pools work, so I'm going to backtrack and explain a little - the question is slightly off target, which is one reason I've not responded earlier. You can have multiple buffer pools, one for each different page size that you use. On a system where IDS uses 2K basic pages, you can have buffer pools for pages of size 2, 4, 6, 8, 10, 12, 14 and 16 KB; for systems where IDS uses 4K basic pages, you can have buffer pools for pages of size 4, 8, 12, 16 KB. Each buffer pool will be used for pages from any dbspaces with the relevant page size. All the buffer pools configured in ONCONFIG will be created on start up; even if you have no dbspaces with the relevant page size, the buffer pool will still be allocated - and will be used when you add a dbspace of the appropriate size. If you add a dbspace with page size 8K, say, and there is no buffer pool for pages of size 8K, then a buffer pool will be created. Note that the critical dbspaces (rootdbs, logical logs, physical log) must all exist in dbspaces of the basic page size; you will always have a buffer pool of 2K (or 4K) on your system. You may also have buffer pools for larger page sizes. Note that buffer pools created at start up will be in the initial shared memory segments - buffer pools added later may (will usually?) be in extension segments. So, the comment about 4MB (system) page sizes on Solaris has no implications for any page size in a buffer pool, but it might have some significance for the number of buffers you specify. However, even so, it is of limited significance, I believe. You might want to ensure that your initial shared memory segment is a multiple of 4MB, but that's about it. -- Jonathan Leffler #include <disclaimer.h> Email: jleffler@earthlink.net, jleffler@us.ibm.com Guardian of DBD::Informix v2005.01 -- http://dbi.perl.org/
Thank you, Jonathan. I guess I was not clear on system vs IDS page size. I knew that the page size for IDS on our Sun boxes was 2K. I didn't know what to make of the mention of 4 MB page size. Why, I thought, would I want to make a buffer pool with page size anything other than the native 2KB? It is my ignorance that motivated the question. Regards, DG