Unmounting and Mounting a SYBASE database

Hello Everyone,

We have 2 instances with some set of databases in each instances . ( Both are with same version and running on same host 15.7 ) .

We would like to move database named as "QWE" (DBID is 6 ) from instance1 to instance2.

But in instance2 , We have set of databases and one of DB is assigned with DBID as 6. Now as i mentioned i would like to move database "QWE" from instance1 to instance2.

I read in manuals as "In destination server DBID slot should be free i.e here DBID 6 ) . But in my case database exists with DBID = 6 in instance2 .

How to UNMOUNT and MOUNT database with new DBID or How to change the DBID of existing database ?.

Please advise on this