Level 1 to level 2 migration

Before automatic secondary space management starts level 1 to level 2 migration, it performs the following checks:

Checks to see there is any command level 1 to level 2 running. If yes, the level 1 to level 2 migration of automatic secondary space management will not start. There is no reason to run two level 1 to level 2 migrations at the same time.
Performs a space check on the all ML1 volumes. If any NOOVERFLOW ML1 volume has an occupancy that is equal to or greater than its high threshold, then all eligible data sets migrate from the NOOVERFLOW ML1 volume to ML2 volumes. For OVERFLOW volumes, the percentage of occupied space for each ML1 OVERFLOW volume will be calculated and then DFSMShsm will compare the average value with the specified threshold. Secondary space management is started for all eligible ML1 OVERFLOW data sets if the overflow volume pool threshold is met or exceeded. If you choose to use OVERFLOW volumes, you can specify the average overflow volume pool capacity threshold at which you want automatic secondary space management to migrate ML1 OVERFLOW volumes to ML2 volumes using the SETSYS ML1OVERFLOW command:
```
SETSYS ML1OVERFLOW(THRESHOLD(threshold))
```
Eligible SMS-managed data sets are those data sets that have passed the value you specified with the LEVEL 1 DAYS NON-USAGE attribute in their management class. Eligible non-SMS-managed data sets are those that have passed the value you specified with the MIGRATIONLEVEL1DAYS parameter of the SETSYS command.

ML2 volumes can be either DASD or tape. The TAPEMIGRATION parameter of the SETSYS command specifies what type of ML2 volume is used. The SETSYS command for DFSMShsm host 2 specifies ML2 migration to tape.

Level 1 to level 2 migration

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