MCDS Scan processing
The scan process is initiated with the MSCAN console command, scheduled service, or with the SMMSYS MSCAN_POST parameter. The process reads the MCDS data sets and creates an output collection data set that contains summary information. The MSCAN collection data set is reused with each MSCAN request and is accessed by the online views and dialogs during reporting. Parameters in SMMSYS specify the allocation information for the data set.
The information created by the MSCAN process is used in ML1 and ML2 reporting views and in management class modeling capabilities. Views available from links on the Data Set Management menu combine this ML1 and ML2 information with information from the VTOC Scan master collection data set, representing ML0, to show space usage, aging, and size analysis across all three HSM storage levels. This usage can be seen from the point of view of your storage groups and pools, management classes, applications, high-level qualifiers, high-level qualifier and group or pool, and high-level qualifier and management class.
The management class modeling tool allows you to estimate the impact of a change to the management class primary day value and the level-1 day value on storage requirements. The tool shows you the storage usage of data sets at ML0, ML1, and ML2 in the current MCDS snapshot. It then allows you to enter different values for the primary days and level-1 days values. The tool then shows the resulting storage requirements that would be needed at each level.
The MSCAN process takes a snapshot of migrated data set information at the time that the MSCAN command is issued. You might consider the best times of day to run this command for both performance and reporting reasons. For example, a snapshot of migrated data set information that is taken after the completion of primary and secondary space management might look very different from a snapshot taken prior to those events starting. BMC recommends running the MSCAN process once a day, shortly after primary space management completes processing. As distributed, a Scheduled Service request in the SMSCHD00 PARMLIB member issues the MSCAN command once a day at 11:30 P.M. Using the SMMSYS MSCAN_POST parameter, you can initiate MSCAN automatically after primary or secondary space management completes processing. For more information about SMMSYS parameters, see Parameters used to tune MSCAN collection performance.
Because the views and modeling tool use both MSCAN and VTOC Scan output, you might consider running a system-wide VTOC Scan shortly before or after the MSCAN process.
The MSCAN process uses a multitasking architecture to reduce the elapsed time that it normally takes to read through an entire MCDS data set. The reduction in elapsed time is at the expense of I/O and CPU percentage, because the same amount of work is now being done in less time. The MSCAN_MXTSK parameter can be used to control the number of tasks used in the process.
For more information, see:
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