Functionally, data being dumped or copied is unavailable only for
the time it takes for DFSMSdss to start a concurrent copy session.
Initialization takes only a matter of seconds to complete successfully.
The session initialization process is a series of distinct steps,
as follows:
- Determine an appropriate time to start a backup of databases,
and stop update activity to those databases.
- DFSMSdss uses concurrent copy to perform a copy or dump of the
data. You can use DFSMSdss directly from JCL or from an application
through the DFSMSdss application interface.
- DFSMSdss locates the data sets to process and breaks them down
into a hierarchy of volumes and extents.
- DFSMSdss interfaces with the system data mover to initialize a
concurrent copy session.
- The SDM determines which storage controls are attached to the
affected volumes and defines a concurrent copy session to each storage
control. The SDM also tells each storage control the volume and the
extents on each volume that are included in this concurrent copy session.
Once the SDM has completely initialized the session, it returns control
to DFSMSdss.
- DFSMSdss checks all SDM return codes. DFSMSdss releases serialization
on those data sets or volumes that were successfully included in the
concurrent copy session. DFSMSdss keeps serialization on data sets
or volumes that are not included in the session.
- DFSMSdss issues messages that indicate the status of the session.
DFSMSdss uses the user interaction module (UIM) to update the calling
program with the status of the session, if the application interface
called DFSMSdss.
- The application can take appropriate action, which may include
restarting applications.