A $$$SPACE member is used by the PDSMAN Dynamic Space Reuse facility to track reusable space within a Partitioned Data Set (PDS). PDSMAN Dynamic Space Reuse does not operate on PDSEs because these libraries perform their own management and reuse of the library space.
For a PDS, PDSMAN creates a $$$SPACE member when the library is compressed and there is a matching PDSMAN $UPDATE rule with PSR=Y specified.
PDSMAN will not create the $$$SPACE member in a PDSE and will not allow a $$$SPACE member to be copied from a PDS under Dynamic Space Reuse to a PDSE. However, it is possible for this member to be inadvertently copied to the PDSE if PDSMAN is not active or does not see the copy operation.
PDSMAN will never use the $$$SPACE member from a PDSE. It is safe to delete a $$$SPACE that was created in a PDS and subsequently copied into a PDSE.