Hi thank you for reading my post, I have one database which is a part of another application which my application should work in relation to it. a problem that i have is something like this: DB1 which is the old (already working ) application database has some tables which my application need thier data. but DB1 tables are always under changes, ( records are comming , updating, and going out of the table) How can my application understand when a record is changed in old tables in order to react to those changes?
So you are looking at some sort of database synchronization or replication tool. These sorts of things tend to be heavy-weight and expensive. Have a google for "database synchronization" to see what's out there.
How do you use the data in DB 1 and what database is it? Do you only need to read from tables? If so some databases allow you to create tables views that are actually tables in another schema, which might avoid the need to use any sort of synchronization.