Basically I want to check how much free space s availbale on DSAD
This is almost as good as asking "How high is up?" Allocation policies are determined by various policies (such as high level qualifier, use of PROD vs TEST, etc) and the different pools might have radically different amounts of free space. The PROD pool having 250 GB of free space does you absolutely no good if you're allocating a TEST pool dataset for which there is no free space. Your storage management admins are the only ones who could possibly help you with a request like this.