The .u.w dictionary is a dictionary of table names and (handle;subscribed syms). Timestored have a tutorial on tick with the example:
q).u.w
quote | ()
trade | ,(396;IBMAA )
Here there is one subscription to the trade table for the IBM and AA symbols on handle 396 and no subscriptions to the quote table. The link to the Timestored tutorial is here: Kdb Tick Data Storage Kdb+ Tutorials (timestored.com)
It may be beneficial for you to try starting tick with a couple of different rdb processes and try different variations using .u.sub. In standard tick the rdb subscribes to all tables and all syms, using .u.sub[ ; ], but you can change this to subscribe to specific tables/syms. The first argument is the table name the second is the list of syms you want to subscribe to. For the example above it would look like:
.u.sub[`trade;`IBM`AA]
It may be helpful for you to see for yourself.