HSMS permits request processing to be controlled so that input from S2 and output to S2 are restricted to specific times. Requests which require volumes of the class “TAPE” to be mounted are processed during a tape session only.
Synchronous processing of action statements which require volumes of the class “TAPE” is likewise permitted during these tape sessions only.
At the beginning of each tape session HSMS checks which of the requests currently waiting in the request file require access to S2 (for a particular archive or for a particular access type, see below). All relevant accesses are processed during the current tape session. Requests that have been received up to this point may be combined in collector requests, if appropriate, in order to accelerate request processing (see section "Collector requests").
Any requests received after the start of a tape session are assigned to the next tape session. The user cannot control the length of the tape session. It depends exclusively on the time required for processing the access requests received.
No tape session is started before the previous one has terminated.
Tape sessions can be defined for the entire system or for individual archives. Tape session control is the exclusive responsibility of the HSMS administrator. This also applies to private archives of other archive owners. The HSMS administrator sets the global system default values by means of the DEFAULT-TAPE-CONTROL operand of the HSMS statement MODIFY-HSMS-PARAMETERS. These values apply to data transfer in general; with regard to the other basic functions, the HSMS administrator can define different values for individual archives by means of the HSMS statement MODIFY-TAPE-CONTROL.
Tape sessions are defined separately for the various types of access and request.
Type of task | Operand | Access type |
Read requests | READ-CONTROL | Input |
Write requests | WRITE-CONTROL | Output |
Express requests | EXPRESS-CONTROL | HSMS administrator I/Os |
Read requests are all requests generated by
IMPORT-FILES
RECALL-MIGRATED-FILES FROM-STORAGE=*ANY/*S2-STORAGE-LEVEL
RESTORE-FILES
RESTORE-NODE-FILES
implicit recall of migrated files