Microsoft® SQL Server 2012 Unleashed

Bulk Changed Map Pages

The eighth page (page number 7), and every 511,232nd page thereafter, in the database file is the bulk changed map (BCM). When you perform a minimally or bulk-logged operation in SQL Server 2012 in BULK_LOGGED recovery mode, SQL Server logs only the fact that the operation occurred and doesn’t log the actual data changes. The operation is still fully recoverable because SQL Server keeps track of what extents were actually modified by the bulk operation in the BCM page. Similar to the DCM page, each bit on a BCM page represents an extent within its range, and if the bit is set to 1, that indicates that the corresponding extent has been changed by a minimally logged bulk operation since the last full database backup. All ...