SQL Server Lock Implementation Levels

SQL Server implements lock granularities at the following resource levels and in
this order:

• Row (RID)
• Key (KEY)
• Page (PAG)
• Extent (EXT)
• Heap or B-tree (HoBT)
• Table (TAB)
• File (FIL)
• Application (APP)
• MetaData (MDT)
• Allocation Unit (AU)
• Database (DB)