What does onstat -g lmx spots?

Hi all, quick question, what does onstat -g lmx tell you? when I face a slow down and I check "onstat -g lmx" output saying there is a pt_# mutex with a holder and a long queue of threads waiting for that resource, does it mean that the thread holding the lock is generating the problem or could be that another different session(s) is running a bad query(s), then that affects to the session holding the mutex and it takes longer to exit from the critical section queueing the rest of the sessions? many thanks in advance Claudio

Just had this one. PT_ mutexes are used to manage access to a partition's tablespace tablespace or partition header page. You would be locking one if your session is modifying any of the information on that page, such as: extent list index keys, number of rows number of pages number of used pages number of data pages etc. Typically these operations are VERY fast and the mutex locking is transient. However, if you have several sessions actively modifying a table (inserting, deleting, creating indexes, compressing, reorging, etc.) there can be some contention for this single resource. There are some things you can do. Fragmenting the table ROUND ROBIN so that the number of concurrent accesses to each of the tables partitions' header page are reduced by a factor of the number of partitions/fragments is one. Changing large insert jobs to use INSERT/PUT cursors with a maximum sized communications buffer (see FET_BUF_SIZE) so that batches of many rows are inserted in a single operation is another. Art Art S. Kagel Advanced DataTools (www.advancedatatools.com) IIUG Board of Directors (art@iiug.org) See you at the 2010 IIUG Informix Conference April 25-28, 2010 Overland Park (Kansas City), KS www.iiug.org/conf Disclaimer: Please keep in mind that my own opinions are my own opinions and do not reflect on my employer, Advanced DataTools, the IIUG, nor any other organization with which I am associated either explicitly, implicitly, or by inference. Neither do those opinions reflect those of other individuals affiliated with any entity with which I am affiliated nor those of the entities themselves. On Tue, Feb 16, 2010 at 9:39 AM, CLAUDIO NAVARRO <claudio.oami@gmail.com>wrote: > Hi all, > > quick question, what does onstat -g lmx tell you? > when I face a slow down and I check "onstat -g lmx" output saying there is > a > pt_# mutex with a holder and a long queue of threads waiting for that > resource, does it mean that the thread holding the lock is generating the > problem or could be that another different session(s) is running a bad > query(s), then that affects to the session holding the mutex and it takes > longer to exit from the critical section queueing the rest of the sessions? > > many thanks in advance > > Claudio > > > > ******************************************************************************* > Forum Note: Use "Reply" to post a response in the discussion forum. > > --00151747857c06bb82047fb8f140