A migrated file can also be recalled without the user issuing an explicit request to HSMS. When a user or user program tries to access a migrated file, the BS2000 Data Management System (DMS) deduces from the catalog entry that the file is not available at the processing level and must first be recalled. If a file is requested with /SECURE-RESOURCE-ALLOCATION with a wait time specification, and if access operations such as OPEN INPUT, INOUT or UPDATE are used, DMS automatically (implicitly) recalls the file.
If the file is recalled implicitly, it is retrieved from the last save file (including copies) on the storage level entered in the catalog.
Implicit recalls are handled differently, depending on whether the file is accessed by means of a SECURE-RESOURCE-ALLOCATION command or an OPEN. A request using the command
/SECURE-RESOURCE-ALLOCATION FILE=<file name>,WAIT=...
with a wait time before the beginning of processing has the following advantages:
All files needed for a job (up to 48) can be addressed with a single command and recalled via a single request. As a result, fewer HSMS calls and possibly fewer tape requests are required.
There is a defined waiting point after which processing either can start or must be aborted. “Unpleasant surprises” caused by missing files during processing can thus be avoided.
For recall requests initiated in this manner, HSMS outputs a summary report which is otherwise output only if errors occur in implicit recall operations.
The length of the wait time specified via the WAIT operand should be selected so that S2 can also be accessed during this period. If no wait time is specified, DMS reports an error in reserving the file.
If the recall request is started following an OPEN, the following cases have to be distinguished:
Recall in interactive mode from storage level S1:
The recall is always executed and no message is output.Recall in interactive mode from storage level S2:
HSMS outputs a message stating that storage level S2 is being accessed and asking the user whether recall is to be started.
If the user confirms the recall request or does not react within the preset wait time, HSMS issues a second message. Following this, HSMS starts the recall operation, which cannot be aborted after this point.
If the user does not confirm the recall request, HSMS does not start the recall operation and access to the file is rejected.The HSMS administrator can influence the behavior of HSMS by deactivating the interrupt mechanism via the CANCEL-AT-RECALL operand of the HSMS statement MODIFY-HSMS-PARAMETERS. This causes HSMS to suppress message output and to start the recall operation without requesting confirmation. The HSMS administrator can also set the maximum wait time to any value between 10 seconds and 60 minutes using the MAXIMUM-WAIT-TIME operand. However, it is advisable to specify a short wait time for the interrupt mechanism.
Recall in batch mode:
The recall is always executed.During a recall, the file is first imported under the storage space of the SYSHSMS user ID before being assigned to the final user ID. The SYSHSMS user ID must therefore have sufficient storage space – even for very large files. That is why the storage space extension function (PUBLIC-SPACE-EXCESS) should be allowed when setting up the SYSHSMS user ID.
If you are working in interactive mode, files are automatically recalled from storage level S2 only during the defined tape sessions; otherwise you will receive a message when accessing a migrated file.
Using the backup server
In HSMS V11.0 and higher, the agreed backup server can be used to implicitly recall files which were migrated from shared pubsets, see section "Backup server"). For this purpose, a relevant value must be set in the relevant pubset environment for the archive attribute BACKUP-SERVER-USAGE of the assigned default system archive
SYSMIGRATE.
In an SF pubset environment, SYSMIGRATE is a pubset-specific migration archive, or, if not defined, a globally defined migration archive. In an SM pubset environment, SYSMIGRATE is always a pubset-specific migration archive.
If defined, the backup server specified in the local system is used when BACKUP-SERVER-USAGE=*STD is set.
If BACKUP-SERVER-USAGE=*‘NO is set, the backup server functionality is not used, even when a backup server is defined in the local system. Processing takes place in master/slave mode.
If no default system archive SYSMIGRATE is defined, the recall also takes place in master/slave mode.