Steve, By "distinct user" do you mean distinct username? Or sid/serial# combination? In my case, we use connection pooling, while there may be up to 300 sessions, they are all the same named user.
Rachel --- Steve Adams <[EMAIL PROTECTED]> wrote: > Hi All, > > Someone has alerted me to this thread, and asked for a comment. > On a quick scan, and it seems to me that you've mostly got it right. > > The "problem" is that when an SQL statement that refers to its base > objects via public synonyms is shared by multiple distinct Oracle > users, > then name resolution and permission checking need to repeated for > each > distinct user, and because the results of these actions are cached on > the shared cursor, they increase the cost of subsequent such > operations. > That is, public synonyms cause extended latch retention as well as > additional latching. > > For example, if 500 distinct users share 200 SQL statements that > refer > 300 times to 100 base tables via public synonyms. Then there will > also > be 100 * 500 non-existent objects in both the dictionary cache and > the > library cache; 200 * 500 cursor authorization structures; and 300 * > 500 > negative dependency records in the library cache. These last two > things > are cached as segmented arrays that are scanned linearly - thus the > increased latch retention. > > If your application doesn't have hundreds of distinct Oracle users, > or if you can afford the extra latch gets and longer latch retention, > then you will probably not notice all of this unless you start doing > library cache dumps. > > That is, the use of public synonyms is a major scalability threat, > but > does not normally cause performance problems. > > @ Regards, > @ Steve Adams > @ http://www.ixora.com.au/ - For DBAs > @ http://www.christianity.net.au/ - For all > > > -- > Please see the official ORACLE-L FAQ: http://www.orafaq.net > -- > Author: Steve Adams > INET: [EMAIL PROTECTED] > > Fat City Network Services -- 858-538-5051 http://www.fatcity.com > San Diego, California -- Mailing list and web hosting services > --------------------------------------------------------------------- > To REMOVE yourself from this mailing list, send an E-Mail message > to: [EMAIL PROTECTED] (note EXACT spelling of 'ListGuru') and in > the message BODY, include a line containing: UNSUB ORACLE-L > (or the name of mailing list you want to be removed from). You may > also send the HELP command for other information (like subscribing). __________________________________ Do you Yahoo!? Yahoo! Hotjobs: Enter the "Signing Bonus" Sweepstakes http://hotjobs.sweepstakes.yahoo.com/signingbonus -- Please see the official ORACLE-L FAQ: http://www.orafaq.net -- Author: Rachel Carmichael INET: [EMAIL PROTECTED] Fat City Network Services -- 858-538-5051 http://www.fatcity.com San Diego, California -- Mailing list and web hosting services --------------------------------------------------------------------- To REMOVE yourself from this mailing list, send an E-Mail message to: [EMAIL PROTECTED] (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB ORACLE-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing).
