DBA_RGROUP lists all refresh groups.

Column Datatype NULL Description
REFGROUP NUMBER   Internal identifier of refresh group
OWNER VARCHAR2(30) NOT NULL Owner of the object in the refresh group
NAME VARCHAR2(30) NOT NULL Name of the object in the refresh group
IMPLICIT_DESTROY VARCHAR2(1)   (Y or N) If Y, then destroy the refresh group when its last item is removed
PUSH_DEFERRED_RPC VARCHAR2(1)   (Y or N) If Y, then push changes from snapshot to master before refresh
REFRESH_AFTER_ERRORS VARCHAR2(1)   (Y or N) If Y, proceed with refresh despite error when pushing deferred RPC's
ROLLBACK_SEG VARCHAR2(30)   Name of the rollback segment to use while refreshing
JOB NUMBER NOT NULL Identifier of job used to refresh the group automatically
PURGE_OPTION NUMBER(38)   The method for purging the transaction queue after each push. 1 indicates quick purge option; 2 indicates precise purge option
PARALLELISM NUMBER(38)   The level of parallelism for transaction propagation
HEAP_SIZE NUMBER(38)   The size of the heap