Object Allocation Map. An Object Allocation Map (OAM) contains information about how space is allocated for Adaptive Server objects. A single OAM page holds information about up to 250 allocation pages (248 if the object is an IDENTITY column). Each allocation page for an object has an entry in the OAM pages for that table or index. The OAM entry for each allocation page stores the number of used and unused data and index pages on that allocation page. A maximum of 263 OAM pages are allowed, supporting a maximum of 65,535 allocation units for an object.