H5P_SET_ATTR_PHASE_CHANGE sets threshold values for attribute storage on an object. These thresholds determine the point at which attribute storage changes from compact storage (i.e., storage in the object header) to dense storage (i.e., storage in a heap and indexed with a B-tree).
In the general case, attributes are initially kept in compact storage. When the number of attributes exceeds
max_compact, attribute storage switches to dense storage. If the number of attributes subsequently falls below
min_dense, the attributes are returned to compact storage.
max_compact is set to
0 (zero), dense storage is always used.
min_dense must be set to
0 (zero) when
ocpl_id is a dataset or group creation property list identifier. The term
ocpl, for object creation property list, is used when different types of objects may be involved.