Drew Wutka
DWUTKA at Marlow.com
Fri Sep 7 08:56:24 CDT 2007
Depends. The shadow database where the live database is updating the test database would have no down time, it would just be a matter of switching to the new system. In the case of the snapshot type, where the test system is developed and tested with a one time snapshot, the down time is going to be the length of time it takes to import the new data. In the case of a mixed environment, the example I gave had a downtime of about 30 seconds. (The time it took me to swap the linked tables with imported tables.) Drew -----Original Message----- From: accessd-bounces at databaseadvisors.com [mailto:accessd-bounces at databaseadvisors.com] On Behalf Of Rocky Smolin at Beach Access Software Sent: Friday, September 07, 2007 8:08 AM To: 'Access Developers discussion and problem solving' Subject: Re: [AccessD] Database Patent Drew: In which of these situations, there would be a brief interruption in service? Rocky -----Original Message----- From: accessd-bounces at databaseadvisors.com [mailto:accessd-bounces at databaseadvisors.com] On Behalf Of Drew Wutka Sent: Thursday, September 06, 2007 10:41 PM To: Access Developers discussion and problem solving Subject: Re: [AccessD] Database Patent To answer your 'shadow' database question, it depends on how the developer wants to set things up. There are lots of methods. The 'test' database with the new design could be a snapshot of the data, so that it is identical at the start, but the live and the test are then separate. In this case, the 'data dump' process is tested and approved, and when the new system is ready, a final data dump is run (may take more then a few minutes depending on the size of the system and speed of the components). We did this recently with our production/manufacturing database. Old system on a Unix box, new system on a windows based platform. Same software (just different versions (years apart). The final data dump, when we were ready to go live, took about 2 hours. (Probably about 50 gigs of data). You could also design a system that runs both at the same time. In a server based OS, triggers could be put in place that would update the 'shadow' server data. Another method would be to create an 'update' script. Where the shadow system is a mirror of the live site, and the done to it is a script that updates the design (modifying data formats as needed), and the final result is when that script is run against the live system. Another method is partial jumpers. Running the new data in a new database and keeping the old data (and format) live in the old system, until you are ready to put the whole new system in place. I did this with the ISFE (a system I built years ago, and recently updated). The new ISFE had only a handful of tables that the old system used. So the new database actually linked those tables while the new system went out. The old system worked, with a few processes stuck with old data, (processes unnecessary in the new system). There were several things that used the old system, however, but they used the linked tables. So while they were still entering data into the old database, the new database saw all that data, because it was using the links. When I was ready to drop the old database, it was a simple matter of importing the linked tables, took a minute, tops. Drew -----Original Message----- From: accessd-bounces at databaseadvisors.com [mailto:accessd-bounces at databaseadvisors.com] On Behalf Of Rocky Smolin at Beach Access Software Sent: Thursday, September 06, 2007 11:18 PM To: 'Access Developers discussion and problem solving' Cc: 'Jack Stone' Subject: Re: [AccessD] Database Patent Shamil: Thanks for your response. So you see nothing unique in this patent? (BTW, the patent is not pending, but has been granted.) Does this look like "old" technology to you? Is it obsolete technology based on what you describe below as the current methods of implementing changes in the datamodel? Just out of curiosity - So during the time that the new datamodel is being tested in the "shadow" database, am I correct in assuming that the real-time changes that are going on in the production database are also happening in the "shadow" database? That it's a mirror? Rocky The information contained in this transmission is intended only for the person or entity to which it is addressed and may contain II-VI Proprietary and/or II-VI BusinessSensitve material. If you are not the intended recipient, please contact the sender immediately and destroy the material in its entirety, whether electronic or hard copy. 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