I use Tamino Manager to check Data storage at
Tamino->Databases-><>->Information->Space Usage → Data Space
However, after I deleting all the document inside Interactive interface by pressing Delete button for node, the data space still remains the same. Why?
I bet if you undefine the schema, the space usage will change. My understanding for the reason for this is as follows.
Tamino preallocates space within the database for the storage of XML documents, and expands this space as and when necessary. When you delete documents in the manner you speak of (using TII), this preallocated space is not freed but left allocated for adding more documents of that particular doctype/schema. It is more efficient this way than constantly re-adjusting space each time a document is added, updated or deleted which would lead to poor performance. Therefore the reason Tamino does this is for both efficiency and performance.
Hope this helps.