number of oam trips

number of oam trips specifies the number of times an object allocation map (OAM) page traverses the MRU/LRU chain before it is considered for swapping out. The higher the value of number of oam trips, the longer aged OAM pages stay in cache.

Summary Information

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Required role

System administrator

Each table, and each index on a table, has an OAM page, which holds information on pages allocated to the table or index and is checked when a new page is needed for the index or table. A single OAM page can hold allocation mapping for between 2,000 and 63,750 data or index pages.

The OAM pages point to the allocation page for each allocation unit where the object uses space. The allocation pages, in turn, track the information about extent and page usage within the allocation unit.

In some environments and benchmarks that involve significant allocations of space (that is, massive bulk copy operations), keeping OAM pages in cache longer improves performance. Setting number of oam trips to a higher value keeps OAM pages in cache.

Note: If the cache is relatively small and used by a large number of objects, do not set number of oam trips too high. This may result in the cache being flooded with OAM pages that do not age out, and user threads may begin to time out.

Before changing the value of number of oam trips to a number other than 0, make sure the application has sufficient cache to store all index, OAM, and data pages. Consult SAP Technical Support before changing the value of number of oam trips.