Why Oracle creates two shared memory segments instead of one?

I noticed that on some platforms Oracle always creates two shared memory segments instead of one, even when both segments are much smaller than the limit. For example, on this Tru64 box the limit is set to 2 GB: oracle > sysconfig -q ipc ipc: msg_max = 8192 msg_mnb = 16384 msg_mni = 64 msg_tql = 40 shm_max = 2147483640 <<<---- Limit set to 2 GB shm_min = 1 shm_mni = 1024 Still Oracle creates two segments: one 8 MB, second 900 MB oracle> ipcs -am Shared Memory: T ID KEY MODE OWNER GROUP CREATOR CGROUP NATTCH SEGSZ CPID LPID ATIME DTIME CTIME m 1024 0x1e34 --rw-rw-rw- root daemon root daemon 4 524288 3679586 4104730 11:32:05 11:32:04 21:14:45 m 2 0 --rw-r----- oracle dba oracle dba 9 8388608 4090358 4115445 8:40:03 8:40:13 10:58:11 m 3 0x1c6492d0 --rw-r----- oracle dba oracle dba 9 947912704 4090358 4115445 8:40:03 8:40:13 10:58:11

On Oct 25, 3:44 pm, Vsevolod Afanassiev <vafanass...@yahoo.com> wrote: > I noticed that on some platforms Oracle always creates two shared > memory > segments instead of one, even when both segments are much smaller than > the > limit. > > For example, on this Tru64 box the limit is set to 2 GB: > > oracle > sysconfig -q ipc > ipc: > msg_max = 8192 > msg_mnb = 16384 > msg_mni = 64 > msg_tql = 40 > shm_max = 2147483640 <<<---- Limit set to 2 GB > shm_min = 1 > shm_mni = 1024 > > Still Oracle creates two segments: one 8 MB, second 900 MB > > oracle> ipcs -am > > Shared Memory: > T ID KEY MODE OWNER GROUP CREATOR CGROUP > NATTCH SEGSZ CPID LPID ATIME DTIME CTIME > m 1024 0x1e34 --rw-rw-rw- root daemon root > daemon 4 524288 3679586 4104730 11:32:05 11:32:04 > 21:14:45 > m 2 0 --rw-r----- oracle dba oracle > dba 9 8388608 4090358 4115445 8:40:03 8:40:13 > 10:58:11 > m 3 0x1c6492d0 --rw-r----- oracle dba oracle > dba 9 947912704 4090358 4115445 8:40:03 8:40:13 > 10:58:11 Just guessing here, but since Oracle doesn't use semaphores on Tru64 ( http://www.oracle.com/technology/products/oracle9i/pdf/Oracle_9i_on_Tru64_UNIX.pdf metalink Note:153961.1 etc.) , I'll bet the little shared memory area is how they do interprocess communication. Try varying the size of things if you can, my prediction is the big one will go up and down, but the little one will stay the same. Of course, they may do everything with sockets since they have to support RAC and clusters, I dunno. jg -- @home.com is bogus. All hail Urey! http://www.nytimes.com/2007/10/25/science/25jacobson.html?_r=1&oref=slogin

Vsevolod Afanassiev wrote: > Still Oracle creates two segments: one 8 MB, second 900 MB What's your Oracle version? ----- �changez opinions et commentaires dans les forums de discussion. http://www.usenetgratuit.com/

"Vsevolod Afanassiev" <vafanassiev@yahoo.com> wrote in message news:1193352285.026233.151260@q5g2000prf.googlegroups.com... >I noticed that on some platforms Oracle always creates two shared > memory > segments instead of one, even when both segments are much smaller than > the > limit. > > For example, on this Tru64 box the limit is set to 2 GB: > > oracle > sysconfig -q ipc > ipc: > msg_max = 8192 > msg_mnb = 16384 > msg_mni = 64 > msg_tql = 40 > shm_max = 2147483640 <<<---- Limit set to 2 GB > shm_min = 1 > shm_mni = 1024 > > Still Oracle creates two segments: one 8 MB, second 900 MB > > oracle> ipcs -am > > Shared Memory: > T ID KEY MODE OWNER GROUP CREATOR CGROUP > NATTCH SEGSZ CPID LPID ATIME DTIME CTIME > m 1024 0x1e34 --rw-rw-rw- root daemon root > daemon 4 524288 3679586 4104730 11:32:05 11:32:04 > 21:14:45 > m 2 0 --rw-r----- oracle dba oracle > dba 9 8388608 4090358 4115445 8:40:03 8:40:13 > 10:58:11 > m 3 0x1c6492d0 --rw-r----- oracle dba oracle > dba 9 947912704 4090358 4115445 8:40:03 8:40:13 > 10:58:11 > Is Tru64 a NUMA implementation ? Is this 10g. There is a NUMA optimizations that does this by default in 10g: check parameter _enable_numa_optimization. -- Regards Jonathan Lewis http://jonathanlewis.wordpress.com Author: Cost Based Oracle: Fundamentals http://www.jlcomp.demon.co.uk/cbo_book/ind_book.html The Co-operative Oracle Users' FAQ http://www.jlcomp.demon.co.uk/faq/ind_faq.html

On Oct 25, 6:44 pm, Vsevolod Afanassiev <vafanass...@yahoo.com> wrote: > I noticed that on some platforms Oracle always creates two shared > memory > segments instead of one, even when both segments are much smaller than > the > limit. > > For example, on this Tru64 box the limit is set to 2 GB: > > oracle > sysconfig -q ipc > ipc: > msg_max = 8192 > msg_mnb = 16384 > msg_mni = 64 > msg_tql = 40 > shm_max = 2147483640 <<<---- Limit set to 2 GB > shm_min = 1 > shm_mni = 1024 > > Still Oracle creates two segments: one 8 MB, second 900 MB > > oracle> ipcs -am > > Shared Memory: > T ID KEY MODE OWNER GROUP CREATOR CGROUP > NATTCH SEGSZ CPID LPID ATIME DTIME CTIME > m 1024 0x1e34 --rw-rw-rw- root daemon root > daemon 4 524288 3679586 4104730 11:32:05 11:32:04 > 21:14:45 > m 2 0 --rw-r----- oracle dba oracle > dba 9 8388608 4090358 4115445 8:40:03 8:40:13 > 10:58:11 > m 3 0x1c6492d0 --rw-r----- oracle dba oracle > dba 9 947912704 4090358 4115445 8:40:03 8:40:13 > 10:58:11 Did you check with oracle support on this one?

Comments embedded. On Oct 26, 2:35 pm, "Jonathan Lewis" <jonat...@jlcomp.demon.co.uk> wrote: > "Vsevolod Afanassiev" <vafanass...@yahoo.com> wrote in message > > news:1193352285.026233.151260@q5g2000prf.googlegroups.com... > > > > > > >I noticed that on some platforms Oracle always creates two shared > > memory > > segments instead of one, even when both segments are much smaller than > > the > > limit. > > > For example, on this Tru64 box the limit is set to 2 GB: > > > oracle > sysconfig -q ipc > > ipc: > > msg_max = 8192 > > msg_mnb = 16384 > > msg_mni = 64 > > msg_tql = 40 > > shm_max = 2147483640 <<<---- Limit set to 2 GB > > shm_min = 1 > > shm_mni = 1024 > > > Still Oracle creates two segments: one 8 MB, second 900 MB > > > oracle> ipcs -am > > > Shared Memory: > > T ID KEY MODE OWNER GROUP CREATOR CGROUP > > NATTCH SEGSZ CPID LPID ATIME DTIME CTIME > > m 1024 0x1e34 --rw-rw-rw- root daemon root > > daemon 4 524288 3679586 4104730 11:32:05 11:32:04 > > 21:14:45 > > m 2 0 --rw-r----- oracle dba oracle > > dba 9 8388608 4090358 4115445 8:40:03 8:40:13 > > 10:58:11 > > m 3 0x1c6492d0 --rw-r----- oracle dba oracle > > dba 9 947912704 4090358 4115445 8:40:03 8:40:13 > > 10:58:11 > > Is Tru64 a NUMA implementation ? It is, at least for newer releases: http://h30097.www3.hp.com/informationlibrary.html > Is this 10g. > > There is a NUMA optimizations that does this by default > in 10g: check parameter _enable_numa_optimization. > I expect this is the answer the OP was looking for. Good eye, Jonathan. > -- > Regards > > Jonathan Lewishttp://jonathanlewis.wordpress.com > > Author: Cost Based Oracle: Fundamentalshttp://www.jlcomp.demon.co.uk/cbo_book/ind_book.html > > The Co-operative Oracle Users' FAQhttp://www.jlcomp.demon.co.uk/faq/ind_faq.html- Hide quoted text - > > - Show quoted text - David Fitzjarrell

-- Regards Jonathan Lewis http://jonathanlewis.wordpress.com Author: Cost Based Oracle: Fundamentals http://www.jlcomp.demon.co.uk/cbo_book/ind_book.html The Co-operative Oracle Users' FAQ http://www.jlcomp.demon.co.uk/faq/ind_faq.html <fitzjarrell@cox.net> wrote in message news:1193497856.691305.33440@d55g2000hsg.googlegroups.com... > Comments embedded. > On Oct 26, 2:35 pm, "Jonathan Lewis" <jonat...@jlcomp.demon.co.uk> > wrote: >> "Vsevolod Afanassiev" <vafanass...@yahoo.com> wrote in message >> >> news:1193352285.026233.151260@q5g2000prf.googlegroups.com... >> >> >> >> >> >> >I noticed that on some platforms Oracle always creates two shared >> > memory >> > segments instead of one, even when both segments are much smaller than >> > the >> > limit. >> >> > For example, on this Tru64 box the limit is set to 2 GB: >> >> > oracle > sysconfig -q ipc >> > ipc: >> > msg_max = 8192 >> > msg_mnb = 16384 >> > msg_mni = 64 >> > msg_tql = 40 >> > shm_max = 2147483640 <<<---- Limit set to 2 GB >> > shm_min = 1 >> > shm_mni = 1024 >> >> > Still Oracle creates two segments: one 8 MB, second 900 MB >> >> > oracle> ipcs -am >> >> > Shared Memory: >> > T ID KEY MODE OWNER GROUP CREATOR CGROUP >> > NATTCH SEGSZ CPID LPID ATIME DTIME CTIME >> > m 1024 0x1e34 --rw-rw-rw- root daemon root >> > daemon 4 524288 3679586 4104730 11:32:05 11:32:04 >> > 21:14:45 >> > m 2 0 --rw-r----- oracle dba oracle >> > dba 9 8388608 4090358 4115445 8:40:03 8:40:13 >> > 10:58:11 >> > m 3 0x1c6492d0 --rw-r----- oracle dba oracle >> > dba 9 947912704 4090358 4115445 8:40:03 8:40:13 >> > 10:58:11 >> >> Is Tru64 a NUMA implementation ? > > It is, at least for newer releases: > http://h30097.www3.hp.com/informationlibrary.html > >> Is this 10g. >> >> There is a NUMA optimizations that does this by default >> in 10g: check parameter _enable_numa_optimization. >> > > I expect this is the answer the OP was looking for. Good eye, > Jonathan. > >> -- >> Regards >> >> Jonathan Lewishttp://jonathanlewis.wordpress.com >> >> Author: Cost Based Oracle: >> Fundamentalshttp://www.jlcomp.demon.co.uk/cbo_book/ind_book.html >> >> The Co-operative Oracle Users' >> FAQhttp://www.jlcomp.demon.co.uk/faq/ind_faq.html- Hide quoted text - >> >> - Show quoted text - > > > David Fitzjarrell >

<fitzjarrell@cox.net> wrote in message news:1193497856.691305.33440@d55g2000hsg.googlegroups.com... >> Is Tru64 a NUMA implementation ? > > It is, at least for newer releases: > http://h30097.www3.hp.com/informationlibrary.html > >> Is this 10g. >> >> There is a NUMA optimizations that does this by default >> in 10g: check parameter _enable_numa_optimization. >> > > I expect this is the answer the OP was looking for. Good eye, > Jonathan. > Lucky timing - one of my clients sent me an email two days ago asking if I knew why one of their machines was giving them 20 segments per instance: then followed up with an email saying they'd found the answer .. they had 18 NUMA groups, so the twenty was one per group, plus one big one, plus one small one See Metalink note 399261.1 -- Regards Jonathan Lewis http://jonathanlewis.wordpress.com Author: Cost Based Oracle: Fundamentals http://www.jlcomp.demon.co.uk/cbo_book/ind_book.html The Co-operative Oracle Users' FAQ http://www.jlcomp.demon.co.uk/faq/ind_faq.html

On Oct 31, 12:54 pm, atulle...@gmail.com wrote: > Please visit my site > > www.oracle10gtraining.blogspot.com Well, I visited it, and feel my time was wasted. All I saw was some poorly written generalities and google ads. Nothing having to do with this thread, so I must conclude you are trying to make money from the ads, a commercial endeavor precluded by the charter of this group. Note that moneygrubbing isn't the primary determinant of spam, but it does put a post clearly into spam territory. That is why this group frowns on posts such as yours, considering them spam, and considering you a spammer. Please people, don't post stuff like this. It refelcts poorly on you. If you must post, put your blog link in your .sig, and post something relevant to the discussion. People might complain about that anyways, but it's ok. See http://www.dbaoracle.net/readme-cdos.htm#subj17 jg -- @home.com is bogus. http://www.clicksmilies.com/s1106/wuerg/vomit-smiley-020.gif