Free space reported by the FAU does not always agree with the SHOW DEVICE command

The FAU reports the degree of fragmentation of the files and free space on a disk. See the Diskeeper Manual, Chapter 4, Fragmentation Analysis Utility , for a full description of the Fragmentation Analysis Utility report. It reports two items: Total Free Space Size and Lost Blks/Extent Cache (or, if run with SYSPRV privilege, Lost Blks Only). These, when added together, reflect the total amount of free space on the disk. Sometimes, on an active disk, the Free Blocks value reported by SHOW DEVICE does not agree with this figure, due to the extent cache and blocks that OpenVMS has marked free, but has not yet marked as allocatable. A discrepancy is especially likely on an OpenVMS Cluster, since each node has a separate extent cache for each disk.

To clear the extent cache and get a correct report of Free Blocks from SHOW DEVICE, request the allocation of a ridiculously large amount of space. For example:

 

              
                
                  
                    $ COPY/ALLOCATION=1000000000 NL: 
                    filename.ext 
                  
                
              
            

 

No copy or allocation is actually completed, but SHOW DEVICE will then report a number of Free Blocks that corresponds to the Fragmentation Analysis Utility report.

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