Draft Document for Review February 7, 2020 3:15 pm 8464ch14_DisasterRecoveryTesting.fm 14.2.2 Method 2: DR Testing using Write Protect Mode on DR clusters This method uses the Write Protect Mode functionality in TS7700 clusters to prevent all write  activity or volume attribute changes to the hardware categories that are  not  in the  Exclude-from-write-protect list in the DR clusters. The only categories that should be in this  list are those categories that are used by the DR host to read and write from DR volumes that  were processed by host cartridge entry on the DR clusters. All other categories (such as the  categories that production volumes belong to), are write-protected on the DR clusters.  This method features the following advantages and disadvantages: GLYPH<SM590000> Advantages: – By enabling Write Protect Mode on the disast er clusters, the cluster prevents the write  at the hardware level even if a job on the DR host tries to mount a production volume  for write on a disaster cluster. – Production data can still be written to the pr oduction clusters, and those clusters can  still copy data to the disaster clusters so that if a real disaster occurs, the data on the  disaster clusters is more up-to-date than if the copying did not occur. – Write Protect Mode can be enabled permanently  on the DR cluster (not just during the  duration of the DR test), which can provide continuous protection from the  overwriting/return-to-scratch processing on the DR host of volumes that are assigned  to categories that are not in the Excluded from Write Protect list. GLYPH<SM590000> Disadvantages: – The Write Protect Mode and Write Protect Exclude categories must be configured  correctly for any data to be written to the DR clusters during a DR test. If they are  configured incorrectly (for example, by defining production categories as being  excluded from write-protect), production data might be overwritten. – No point-in-time simulation occurs. The data on the volumes that are used during a DR  test can change if those volumes are written to by a production system on a production  cluster and those changes are propagated to the disaster clusters. Jobs that are  running on the DR host that are reading data from production volumes on the DR  clusters might fail if they do not account for this possibility.  If you determine that FlashCopy for DR is not suitable to your DR environment, the use of this  method is the recommended alternative.  14.2.3 Method 3: DR testing without the use of Write Protect Mode on DR  clusters This method is similar to the previous method. However, instead of the use of the Write  Protect Mode functionality in the DR clusters to prevent any writes that are issued from the  DR host to a production volume on the DR clusters, this method relies on the ability (and  correct configuration) of the tape management system (TMS) on a DR host to prevent  volumes in the production volume range from being written to by the DR host. This method features the following advantages and disadvantages: GLYPH<SM590000> Advantage: Production data can still be written to the production clusters and those  clusters can still copy data to the disaster clusters so that in the event of a real disaster,  the data on the disaster clusters are more up-to-date than if the copying did not occur. 772  IBM TS7700 Release 5.0 Guide