To avoid 2 developers working on the same package at the same time:
1) Use your version control system as the source of the package code. To work on a package, the developer must first check out the package from version control; nobody else can check the package out until this developer checks it back in.
2) Don't work directly on the package code in Toad or any other IDE. You have no clue whether the code you are working on there is correct or has been modified by one or more other developers. Work on the code in the script you have checked out from version control, and run that into the database to compile the package. My preference is to use a nice text editor (TextPad) and SQL Plus, but you can do this in Toad too.
3) When you have finished, check the script back into version control. Do not copy and paste code out of the database into your script (see point 2 again).
The downside (if it is one) of this controlled approach is that only one developer at a time can work on a package. This shouldn't be a major problem as long as:
- You keep packages down to a reasonable size (in terms of WHAT they do, not how many lines of code or number of procedures in them). Don't have one big package that holds all the code.
- Developers are encouraged to check out code only when ready to work on it, and to check it back in as soon as they have finished making and testing their changes.