Any answers to this question will tend to have "can", "worms" and "of" in there somewhere :-)
Whenever you refresh a DBMS table what happens is that MapInfo reruns the query used to create it in the first place and overwrites what it had before. You can increase the refresh speed in two ways - make the query run on a smaller dataset (eg don't retrieve all the attribute data) or adjust the query so that it returns fewer rows (eg, only related to a small geographical area where the user is currently working). This is of course aside from all the tuning issues which can improve database performance. Using queries to get the changes only - ie NOT overwriting the table completely - and then apply those changes on the client - is much more complex than it sounds. You're tracking updates, deletions and additions and there are whole realms of issues around that. You could have all the users open the spatial data for 'live' access - register the table rather than opening it. This gives you optimum data currency and pretty good performance - as you say the amount of data needed to display a layer on screen can be small. If you use the cache option it will go quicker since the client only goes back to the database when you move out of the 'cached' area on screen - but it sounds like you want to keep the connection off. Coincidentally we're just doing some work on similar speed/currency issues - as always it depends what your requirement is. You may for example have lots of essentially static backdrop data which you don't need to keep in Oracle at all. This can go on your file servers. It will reduce your refresh times by reducing the amount of spatial data held in Oracle. This is what we are doing with an app where there is a lot of large-scale data currently in the database but which changes much more slowly than the customers own spatial data. Its not as nice as having everything in one place for all users but the speed enhancement makes it worthwhile. HTH Paul Crisp Syntegra Direct: 0191 461 4522 Mobile: 0776 414 3762 Fax: (0191) 461 1959 Innovation Place Metro Riverside Park Delta Bank Road Gateshead Tyne & Wear NE11 9DJ -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]] Sent: 10 January 2002 10:55 To: [EMAIL PROTECTED] Subject: MI-L MB-Oracle question Hi List, I have a simple (I hope) MB-Oracle question.... I have a MB application which connects to a remote Oracle database, links to the required tables, saves them in MapInfo format on the local machine, and closes the connection (the amount of data is not so great). The idea being that the user only has to connect to the Oracle database when they want to update the locally stored tables. At the moment, if the user chooses to access data from the Oracle database, the local MapInfo tables are overwritten. My question is, if changes have been made in the database (new/altered records) does anyone have suggestions as to the best (quickest) way to update the local tables without rewriting the entire tables? I realise I can use the Server Refresh statement to update the tables, but my understanding is that this command erases the files and recreates them. Is the alternative to first execute a SQL query on the database for records created/modified after a certain date (the last connection to the database), then add to/alter the local tables accordingly through a series of queries and updates, or is there an easier method? Cheers, Steven Kalma Integrated Data Solutions _______________________ URS Dames & Moore Treubstraat 33, 2288EH, Rijswijk. The Netherlands +31 (0)70 336 90 89 (direct) +31 (0)70 319 21 12 (switch) +31 (0)6 53 42 89 76 (mobile) +31 (0)70 319 11 25 (fax) [EMAIL PROTECTED] www.urscorp.com/europe _______________________ _______________________________________________________________________ List hosting provided by Directions Magazine | www.directionsmag.com | To unsubscribe, send e-mail to [EMAIL PROTECTED] and put "unsubscribe MapInfo-L" in the message body. ******************************************************************** This email may contain information which is privileged or confidential. If you are not the intended recipient of this email, please notify the sender immediately and delete it without reading, copying, storing, forwarding or disclosing its contents to any other person Thank you Check us out at http://www.syntegra.com ******************************************************************** _______________________________________________________________________ List hosting provided by Directions Magazine | www.directionsmag.com | To unsubscribe, send e-mail to [EMAIL PROTECTED] and put "unsubscribe MapInfo-L" in the message body.
