When you must discard a block or a record, take steps to preserve or create structures that have integrity.

DSE has no single command that discards a block. You must locate the last block in its path with FIND [-BLOCK] or FIND -EXHAUSTIVE and REMOVE the record that points to the block being discarded. Then MAP the deleted block -FREE.

When you discard the only record in any block you must MAP that block -FREE and REMOVE the record (up one level) that points to the deleted block. The only exception is when it is the only block pointed to by the root block of the tree. Leaving empty blocks (except as the data level of empty or undefined globals) violates standard operating assumptions of GDS databases.

When you must discard the top block in a Global Variable Tree, you can alternatively use the method employed by GT.M when it processes a KILL command. This method maintains a record of the global variable name. To use this method, use FIND -FREE to locate a free block, and MAP the new block -BUSY. Next, CHANGE the new block -BSIZ=header-size (7/8) -LEVEL=0. Finally, CHANGE the top level block -BSIZ=header-size (7/8) -LEVEL=1 and ADD -STAR -POINTER=the-new-block.

Never delete the only remaining record in block one (1). Block one (1) is the root block of the Directory Tree for the entire file.