Great points from Wol, as always. What kind of /tmp disk space do you have on this system? (Assuming that /tmp is where UV does some of it's SELECT scratch pad intermediate writing when processing large queries, consult your sites actual uvconfig for all of your actual values...).
If this /tmp is small, single physical disk, or heavily fragmented, this would also contribute to poor query runtime performance. Ditto on your system's swap space, which should be at least 2X physical memory. Wol's approach of breaking down the query into selecting smaller groups of data is a great one. Chip away at the stone, methodically, consistently, and constantly. What platform is this on? What OS version? What UV Version? How much memory & disk space? How much /tmp and swap space? Are you running this query with other users on the system, who may be also trying to access the files this query is working with? Are you runing this at night when it might conflict with a backup operation? More food for thought. Regards, Scott ----- Original Message ----- From: "Anthony Youngman" <[EMAIL PROTECTED]> To: "U2 Users Discussion List" <[EMAIL PROTECTED]> Sent: Monday, March 15, 2004 4:02 AM Subject: RE: Help Needed regarding performance improvement of delete query This might help speed things up a bit ... Firstly, of course, is your file properly sized? Secondly, (and in this case you will need to run the SELECT / DELETE sequence several times) try putting a SAMPLE 1000 (or whatever number makes sense) at the end of your select. Basically, this will mean that the SELECT runs until it finds that number of records and then stops. So each sequence won't load the system so badly. Creating a huge select list will stress your ram badly ... looping through this sequence won't stress the system so badly, though you really do need to use indices to reduce the stress even more ... Create an index on various fields that you're using as your select criteria. If you're selecting old records, then you need to select on date, and this really will make life both easy and fast. The more closely you can guarantee that a select, acting on a single index, will pick up only or mostly records that you are going to delete, the better. That will SERIOUSLY reduce the time taken and the performance hit. Cheers, Wol -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of ashish ratna Sent: 15 March 2004 08:25 To: [EMAIL PROTECTED] Subject: Help Needed regarding performance improvement of delete query Hi All, We are working for purging of old data from the database. But we are facing performance problems in this. We are using select query which is created dynamically on the basis of number of records. We want to know if there is any limit for size of query in Universe. Although in universe help pdf it is mentioned that there is no limit for the length of select query. But when we run the program on the file with records more than 0.5 million it gave the error- "Pid 14433 received a SIGSEGV for stack growth failure. Possible causes: insufficient memory or swap space, or stack size exceeded maxssiz. Memory fault(coredump)" If there is no limitation on the size of query then please suggest some other possible solution which can help us reducing the time of query and completing the process successfully without giving the error. Thanks in advance. Regards, Ashish. **************************************************************************** ******* This transmission is intended for the named recipient only. It may contain private and confidential information. If this has come to you in error you must not act on anything disclosed in it, nor must you copy it, modify it, disseminate it in any way, or show it to anyone. Please e-mail the sender to inform us of the transmission error or telephone ECA International immediately and delete the e-mail from your information system. Telephone numbers for ECA International offices are: Sydney +61 (0)2 9911 7799, Hong Kong + 852 2121 2388, London +44 (0)20 7351 5000 and New York +1 212 582 2333. **************************************************************************** ******* -- u2-users mailing list [EMAIL PROTECTED] http://www.oliver.com/mailman/listinfo/u2-users -- u2-users mailing list [EMAIL PROTECTED] http://www.oliver.com/mailman/listinfo/u2-users
