Boosted Partition Free Space Caches (PFSC)

When MAX_FILL_DATA_PAGES is set, a small cache is automatically created in memory for each table with variable-length rows. The purpose of this "lite" PFSC is to track exactly how much free space exists on up to 32 pages from which rows have recently been deleted. This information can be searched very quickly when inserting a row. If a spot for the new row is found on a page being tracked by the cache, the row is inserted on that page. If not, the table's bitmaps will have to be consulted, which may be less efficient in some cases.

A boosted PFSC is a cache that tracks all free space in the table or fragment. All inserts to this table use this larger cache in lieu of the bitmaps. This feature can significantly improve insert performance, though additional memory is required.

Consider creating a boosted PFSC for a table under the following conditions:
  • The table is either compressed or its schema contains variable-length columns
  • The table is relatively large
  • The table is relatively volatile, with deletes affecting rows of all ages

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