title: WinDbg/SOS: Explanation of !SyncBlk output
body: <p>I am looking of a description of the output generated by the !SyncBlk command of SOS.</p>
  
  <p>Particularly I found no useful explanation on the column "MonitorHeld". This column shows high values in a series of crash dumps.</p>
  
  <p>Example:</p>
  
  <pre><code>0:000&gt; !SyncBlk
  Index         SyncBlock MonitorHeld Recursion Owning Thread Info          SyncBlock Owner
     44 0000000005a5c228            1         1 000000000e7a6740  2304 273   000000019f858cd0 System.Object
     48 000000000579bae8            1         1 000000000e7a72e0  2370 275   000000015f999900 System.Object
     52 000000000579b9c8            1         1 0000000011bbd3b0  1e98 295   00000000ff89fe08 System.Object
     54 000000000579b938            1         1 000000000e7a38c0  1be4 249   000000013f8aa888 System.Object
    108 0000000005a5bfe8            1         1 000000000e79f300  224c 242   00000000ff8a5828 System.Object
    110 0000000005a5c078            1         1 000000000e79ca50  2290 262   000000015f9a8020 System.Object
    112 0000000005a5c108            1         1 0000000011bb70e0  1d38 236   000000015f99e408 System.Object
    114 000000000579b620            1         1 0000000011bb93c0  1884 304   00000001bf974a90 System.Object
    124 0000000005a44d48            1         1 000000000e7a6170  2300 272   000000019f853fe8 System.Object
    146 0000000005a44688           99         1 000000000588cbf0  13e0  38   000000017f71c4f8 System.Object
    155 0000000005a44f88            1         1 0000000011bba530  2274 301   000000019f82f120 System.Object
    157 0000000005a45018            1         1 0000000011bbf0c0  2034 290   000000015f952980 System.Object
  </code></pre>
  
  <p>Can anyone explain the "99" in column "MonitorHeld"?</p>
  
  <p>Has anyone a a link to a complete reference documentation of this command?</p>
  
  <p>Thanks,
  Alex</p>