Our vob storage is growing so rapidly. We used to scrub once a week but nowadays we have to scrub every 8 hrs what could have created this problem? what are the ways to control this? what logs can I look into?
Aside from what has been said previously by VonC, I would also invite you to look at your storage pools.
As you know, the vob storage is made of 3 type of pools (source storage pool, cleartext storage pool, and derived object pool) See IBM page about pool storage
The source storage pool can increase more than usual if you tend to check in more elements version than usual, especially large binary files for example.
The cleartext pool can increase more than usual if you create a lot temporary cleartext data. Typically if you set up a script that access all the files of the VOB, you will generate a lot of cleartext.
The derived object pool increase if you generate a lot of DOs (derived objects) via clearmake or if a lot of derived objects created on the clients are promoted to the server. You may want to check if you perform winkin and if the views created share their DOs.
So I would suggest you to monitor which pool is increasing the most (s\sdft, c\cdft or d\ddft). It will give you a hint about what is happening in your VOB.