Smoke and Mirrors - The New and Improved Capture

Talk to any TPF operator about Capture, and you’ll pretty much get the same feedback. It’s a pain in the behind. With TPF databases growing by leaps and bounds, traditional TPF Capture presents the user with more and more issues to deal with. Scheduling becomes critical, tape drive availability is problematic, CPU cycles become more expensive, and the window in which to run Capture is constantly shrinking. With data integrity more important than ever, it would be nice if there was a way to improve all of these things while still meeting the challenge of backing up your production DASD. Well, there is a better approach to traditional TPF Capture, and the answer is simply… don’t do it.

EMC Corporation has a software product called TimeFinder that addresses all of these issues. Available for several years now, TimeFinder has proven to be the ideal solution for rapid database backups in mainframe and open system environments. By utilizing EMC’s TimeFinder, mainframe users in particular have realized major savings in terms of both time and resources when backing up their critical data.

How It Works

EMC’s use of Business Continuance Volumes (BCV’s) is the primary difference between traditional TPF Capture and TimeFinder. These BCV devices are Symmetrix devices that are specially configured in the Symmetrix control unit as dynamic mirrors. Each BCV has its own host address and is configured as a stand-alone device.

A business continuance (BC) sequence first involves setting, or "establishing", the BCV device as an additional mirror of a standard (i.e. TPF module) Symmetrix device. Once the BCV is established as a mirror of the standard device it is not accessible through its original device address. The BCV device may later be separated, or split, from the standard Symmetrix device with which it was previously paired. The BCV device now has valid data, and is available for use through its original device address. Once host processes on the BCV device are complete, the BCV may again be mirrored to a standard Symmetrix device for the purposes of acquiring new data for other BC processes or updating the standard device with the data from the completed BC processes.

So what does this mean in English? By establishing the BCV’s with the "standard" TPF modules, TimeFinder copies all of the data from the TPF packs to the BCV’s. Once the establish is done, the BCV’s can then be "split", and you now have a complete "capture" of your online database. Since the BCV’s all have unique device addresses, they can (for example), be attached to another processor for use by the customer to accomplish things like:

  • Refreshing your Test System databases
  • Quality Assurance testing
  • Problem analysis and resolution
  • Batch type processing and report generation
  • Copying the BCV’s to tape for archival purposes without the time or resource constraints

The possibilities are limited only by the user’s imagination. What’s important to note is that the entire establish and split process takes place within the Symmetrix. So what you have with TimeFinder is:

  • disk-to-disk copies which are considerably faster than writing to tape
  • no need for Capture tape drives on your production system
  • no CPU cycles needed for copies since all activity takes place in the Symmetrix, and
  • very fast refresh capabilities for your test and development systems

From a time-saving perspective, TimeFinder will "smoke" traditional TPF Capture. Depending on your particular configuration TimeFinder can shave hours off your usual Capture time, and eliminate the scheduling issues many TPF shops face today. Additionally, Exception Recording becomes a minimal effort. With TimeFinder’s split processing taking only minutes, XCP recording is reduced to only one or two tapes (again depending on your particular configuration), instead of running for hours during traditional Capture.

D/R Concerns?

Disaster Recovery is by no means a trivial topic. TimeFinder for TPF, when coupled with EMC’s Symmetrix Remote Data Facility (SRDF) almost certainly provides a better D/R solution than you have today, and does bear mentioning as additional food for thought. Since SRDF does warrant it’s own discussion, it will be addressed in detail in a future article.

TimeFinder for TPF

Announced for general availability in August 1999, "TimeFinder for TPF" version 3.3.0 now provides a robust TPF Operations interface. All of TimeFinder’s configuration and command processing is now managed directly from the TPF Prime CRAS console. Complete control of TimeFinder is available to the TPF Operator via conventional Z-messages to initiate and monitor all of TimeFinder’s features:

TimeFinder Keypoint Record Initialization

This set of commands uses information retrieved through interrogation of TPF and the Symmetrix in the TPF complex, and user defined Symmetrix configuration information to initialize the data structures used by TimeFinder. Initialization determines the BCV pairs that are to be operated upon by subsequent TimeFinder operations.

Establishing a BCV pair

This command assigns the BCV as the next available mirror of a standard Symmetrix device and copies the entire contents of the standard device to the BCV.

Splitting a BCV pair

This command splits the BCV mirror from the standard Symmetrix device and makes it available (with the data from the standard device with which it was paired) to hosts through its separate device address. In a production TPF environment Exception Recording should be started on all processors in the complex prior to issuing a split, and stopped once the split has completed. To ensure a consistent point in time copy, Exception Restore should be run on the BCV system.

Reestablishing a BCV device

This command reassigns the BCV as the next available mirror of the standard device to which it was assigned before it was split. Any data written to the BCV while it was split from the standard device is overwritten on the BCV. The BCV receives its updates from the standard device.

Restoring from a BCV device

This command assigns the BCV as the next available mirror of a standard device and copies the entire contents of the BCV to the standard device. TimeFinder keypoints should reflect the TimeFinder configuration in existence at the time of the Establish.

Incrementally restore from a BCV device

This command reassigns the BCV as the next available mirror of the standard device to which it was assigned (Restore, Establish, or Re-establish) before it was split. Any data written to the BCV while it was split from the standard device is overwritten on the standard device. Any updates made to the standard device while the BCV pair was split are discarded.

Automation Anyone?

Console automation is alive and well at most TPF installations. With minimal effort, users can create automation scripts to manage and monitor all TimeFinder operations. By establishing automation procedures for TimeFinder, you have the added advantage of an "error-free" process for capturing your production database whenever necessary.

Time Is Money

When you consider all of the benefits that can be realized with TimeFinder for TPF, it’s easy to see that EMC has brought new meaning to the expression "smoke and mirrors". Saving hours and hours of time every day that Capture runs adds up to a significant amount of time. Factoring those savings into an annual Operations budget means a better bottom line for your organization, and your company.

More information on TimeFinder for TPF, and how your installation can benefit from it is available by contacting your local EMC representative.