Re: Is dirty read enough ?

Posted in 2003

ART KAGEL, BLOOMBERG/ 65E 55TH — Mon, 23 Jun 2003 08:54:44 -0400 — source: Usenet: comp.databases.informix

> THIS IS A MESSAGE IN 'MIME' FORMAT. Your mail reader does not support MIME. > Some parts of this will be readable as plain text. > To see the rest, you will need to upgrade your mail reader. --PART.BOUNDARY.2960.4671.p057.1056372883.3930 Content-Type: text/plain Content-Transfer-Encoding: 7bit Content-ID: <2960_4671_1056372883_570@inet3-p057> ----- Original Message ----- From: Xiaofeng Chen <xchen@boco.com.cn> At: 6/23 6:58 > Hi, everyone , Hi, > Here I encounter a problem, in our system some tables were accessed > by many clients at the same time. In order to increase > concurrence and prevent influence with each other, we add "set lock mode > to wait" and "set isolation to dirty read" in our client code, > and in server side, we change the lock mode from page to row for the > tables , fragments the tables for distributing read/write operations, > add detached indexs instead of non-detached for tables. > But, I still wonder if it's enough, can it prevent system locks for > the index/table which will affect our clients? What is a 'system' lock? > If IDS wants to adjust the indexes according to data insertion, does it > affect the whole table?, and if it dose, how long will it take ? When the BTree Cleaner threads need to realance the tree and/or merge empty and sparse nodes due to deletes this is done by locking only the affected nodes and these locks are transient lasting a fraction of a second. Your SET LOCK MODE TO WAIT is sufficient to avoid any problems this may cause. Art S. Kagel > > Any comments are appreciated. > Michael. --PART.BOUNDARY.2960.4671.p057.1056372883.3930 Content-Type: application/octet-stream; name="13536152.htm" Content-Transfer-Encoding: 7bit Content-Disposition: ATTACHMENT; filename="13536152.htm" Content-ID: <2960_4671_1056372883_571@inet3-p057> <html xmlns:o="urn:schemas-microsoft-com:office:office" xmlns:w="urn:schemas-microsoft-com:office:word" xmlns="http://www.w3.org/TR/REC-html40">; <head> <META HTTP-EQUIV="Content-Type" CONTENT="text/html; charset=us-ascii"> <meta name=ProgId content=Word.Document> <meta name=Generator content="Microsoft Word 10"> <meta name=Originator content="Microsoft Word 10"> <link rel=File-List href="cid:filelist.xml@01C339B6.E70E21C0">  <style>  </style>  </head> <body lang=ZH-CN link=blue vlink=purple style='tab-interval:21.0pt;text-justify-trim: punctuation'> <div class=Section1 style='layout-grid:15.6pt'> Hi, everyone , <o:p></o:p> <o:p> </o:p>    Here I encounter a problem, in our system some tables were accessed by many clients at the same time. In order to increase<o:p></o:p> concurrence and prevent influence with each other, we add “set lock mode to wait” and “set isolation to dirty read” in our client code, <o:p></o:p> <span lang=EN-US style='font-size:9.0pt;mso-bidi-