As you know JBoss is a purely filesystem based installation. To install you simply unzip a file and thats it. Once you install a certain folder structure is created by default and as you run the JBoss instance for the first time, it creates additional folders for runtime operation. For comparison here is the structure of JBoss AS 7 before and after you start for the first time
Before
jboss-as-7
|
|---> standalone
| |----> lib
| |----> configuration
| |----> deployments
|
|---> domain
|....
After
jboss-as-7
|
|---> standalone
| |----> lib
| |----> configuration
| |----> deployments
| |----> tmp
| |----> data
| |----> log
|
|---> domain
|....
As you can see 3 new folders are created (log, data & tmp). These folders can all be deleted without effecting the application deployed in deployments folder unless your application generated Data that’s stored in those folders. In development, its ok to delete all these 3 new folders assuming you don’t have any need for the logs and data stored in “data” directory.
For production, ITS NOT RECOMMENDED to delete these folders as there maybe application generated data that stores certain state of the application. For ex, in the data folder, the appserver can save critical Tx rollback logs. So contact your JBoss Administrator if you need to delete those folders for any reason in production.