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512 IBM System Storage DS6000 Series: Copy Services with IBM System z
Concurrent Copy, application processing is interrupted for only a minimum time while the
system initializes the Concurrent Copy session. Once Concurrent Copy is active, your
applications continue to process the data, while it is being backed up using Concurrent Copy.
Concurrent Copy provides point-in-time data consistency. The system serializes access to
the data being dumped or copied just long enough for the Concurrent Copy session to be
initialized. This serialization takes a very short time to complete, and this process ensures the
point-in-time copy will be consistent, while the copy is being done with your applications
running.
Concurrent Copy operation
For details about the operation of Concurrent Copy, refer to z/OS DFSMS Advanced Copy
Services, SC35-0428.
Invoking Concurrent Copy
Concurrent Copy (CC) can be invoked by either the DFSMSdss or the DFSMShsm™
functions. IMS™, CICS®, DFSMSrmm™, and DB2 can use CC for their backups.
DFSMSdss has the option of using Concurrent Copy when data sets are copied or dumped.
To invoke Concurrent Copy, the CONCURRENT keyword must be specified on a DFSMSdss
COPY or DUMP commands.
With DFSMShsm, system-managed data can be backed up automatically with Concurrent
Copy by use of management class parameters. DFSMShsm also allows Concurrent Copy to
be used when copying data using Aggregate Backup and Recovery Support (ABARS).
Using the CONCURRENT control statement of the DB2 COPY utility, you can invoke
Concurrent Copy to make a full image copy. During recovery, DB2 can automatically use the
most recent image copy and then apply records from the log.
Concurrent Copy requires the software support provided in DFSMS/MVS. For details on
using Concurrent Copy with these products, refer to the appropriate product manual.
Concurrent Copy on the DS6000
Concurrent Copy is initiated using the CONCURRENT keyword in DFSMSdss or in
applications that internally call DFSMSdss as the copy program, such as the DB2 COPY
utility.
The SDM establishes a Concurrent Copy session with the DS6000. There can be up to 64
sessions active at a time per DS6000 logical subsystem (LSS).
Concurrent Copy and FlashCopy
Concurrent Copy and FlashCopy can coexist in the same DS6000.
If DFSMSdss is instructed to do a Concurrent Copy by specifying the CONCurrent (CC)
keyword, and the copy is for a full volume (DFSMSdss COPY FULL command), the following
will be honored based on whether FlashCopy is installed:
Note: Many of the benefits of using Concurrent Copy also apply to using FlashCopy, with
the added benefits of not using host resources (channel bandwidth, memory). However
you will need to allow for FlashCopy space in your disk subsystems. You will need to
decide which technique offers the best return for your business requirements.