If a volume set is to be added to an SM pubset, the corresponding user task calls the HSMS interface DHSEMPV. DHSEMPV checks whether the volume set is declared as an SF pubset for HSMS:
If the volume set is declared as an SF pubset for HSMS, it cannot be added to an SM pubset (see also section "Converting an SF pubset to a volume set of an SM pubset").
If the volume set is not declared as an SF pubset for HSMS, it can be added to an SM pubset. The saturation level of the new volume set is checked asynchronously.
If a volume set is to be removed from an SM pubset, again the corresponding user task calls the HSMS interface DHSEMPV, which checks whether the volume set to be removed belongs to the S1 level of the SM pubset. The following cases are possible:
The volume set to be removed is explicitly set as S1 level. In this case HSMS implicitly executes a MODIFY-SM-PUBSET-PARAMETERS with S1-VOLUME-SET= *UNDEFINED. This means that an S1 level is no longer defined for the SM pubset.
The volume set to be removed is under HSMS control, and because of the *ALL-HSMS-CONTROLLED setting belongs to the extended S1 level. In this case HSMS checks whether further volume sets under HSMS control are still available for the S1 level. Only if no further volume set is available does HSMS explicitly execute a MODIFY-SM-PUBSET-PARAMETERS with S1-VOLUME-SET= *UNDEFINED. This means that an S1 level is no longer defined for the SM pubset.