I was at a customer recently who was trying to set up MQ for the first time. However the MQ logs and page sets were defined, they came out wrong because the System Managed Storage (SMS) knew best and kept overriding the definitions. The MQ person did not know what SMS was or how it helped them.! I was able to help explain the magic and mystery of SMS, by saying, ( as on TV) here is a document I prepared earlier.
I'll blog another time what definitions we used.
System Managed Storage(SMS)
z/OS systems can have thousands of DASD volumes and managing this could be a big task. For example the person responsible for the z/OS system
may want to put the production data sets for CICS, MQ and DB2 on the newest and fastest DASD available, and put datasets used by developers on older slower DASD.
needs to decide which datasets get backed up, and how often.
SMS can help you manage this. There is normally a role of Storage Manager who sets up and manages the SMS environment. This role is usually transparent to most users of the system.
You can group DASD volumes into pools. For example you might create the following pools
FASTCICS with the volumes FAST01, FAST02 and FAST06
FASTDB2 with volumes FAST04, FAST15 and FAST27
USERPOOL with volumes SLOW45 and SLOW52
You can set up rules so that from the data set name or other information, the rules specify which pool is to be used. So for all user data sets the rules might give USERPOOL, and SMS will allocate a dataset on the volumes in the pool, perhaps on the DASD with the most free space.
CICS datasets would use the pool FASTCICS, and SMS would allocate the datasets within this pool.
Datasets managed by SMS
You can have the majority of your data sets managed by SMS, but data sets like SYS1.PARMLIB and other SYS1.* datasets should not be SMS managed as they are needed at IPL time before the SMS address space has started.
Datasets managed by SMS have characteristics (which are set up by the Storage Manager)
Data class – this is information such as default size for allocation, is it fixed block or variable blocked format?
Storage class - this is information about the DASD to be used. For example you can specify a storage class requires highly available DASD, or particular performance characteristics.
Management class – this is information on how often the data is backed up, how many backups to keep, is the data set to be migrated to tape after a period with no use etc..
When you allocate a dataset, you can specify the above classes in JCL or in IDCAMS, for example MGMTCLAS=,STORCLAS=, and DATACLAS=, on the JCL DD statement.
SMS uses automatic class selection (ACS) to specify or override what has been specified.
For example for a data class the file might include
FILTLIST DB2V10 INCLUDE(DSNDBCP.**)
WHEN (&DSN = &DB2V10 AND &DATACLAS = ' ') DO
SET &DATACLAS = 'EXTENDED'
So a data set with high level qualifier of DSNDBCP would have DATACLAS set to EXTENDED, unless a data class had been specified when it was allocated.
When we allocated a data set, it told us what was used, for example
IDC0181I STORAGECLASS USED IS STRIPED
IDC0181I MANAGEMENTCLASS USED IS NOBACKUP
IDC0181I DATACLASS USED IS STRIPED
An authorised person can use ISMF( Interactive Storage Management Facility) panels in ISPF to display and to change these classes.