In Figure
When you perform delta resync operation, first the journal data in the primary site B are copied to the URz secondary site by journal copy. In this journal copy, only the journal data which is not yet restored to the secondary data volume in the URz secondary site are copied in chronological order. When the journal copy completes, journal restore takes place in the URz secondary site.
In delta resync operation, the status of the URz pair will not change to Pending Duplex but Duplex. This is because delta resync operation copies only the really necessary data by journal copying. Compared to the usual way which copies the whole data in the primary data volume, delta resync operation requires shorter time for the recovery of the URz pair after a failure occurs.
Note: When the total capacity of stored journal data exceeds 80% of the journal volume of TCz Synchronous secondary site, old journal data will be deleted automatically. Therefore, if the total capacity of the journal data which is not restored to the URz secondary data volume exceeds 80% of the journal volume, the secondary data volume will not be able to be restored completely by copying the journal data to the restore journal volume in the URz secondary site. In that case, according to the setting of the journal group option, whole data in the primary data volume will be copied to the secondary data volume, or delta resync operation finishes without any processing.
Usually, if the pair between TCz Synchronous primary site and secondary site is synchronized periodically, the total capacity of the journal data which is not restored to the URz secondary site will not exceed 80% of the journal volume. Though, for example if the URz pair is suspended and the pair has not been resynchronized for a long time, journal data of more than 80% of the journal volume capacity may be stored before they are restored to URz secondary data volume. In such case, note that you may not perform delta resync operation properly.
Warning: Even if the capacity of the journal data does not exceed 80% of the journal volume, note that journal data will or may be destroyed in the following cases.
•When you restore the TCz Synchronous pair, then updated the
•When you restore the URz pair between the primary site and the URz secondary site, then updated the
•When the retry processing occurs because of a delay of the
•When the update of the TCz Synchronous
Chapter 3 Preparing for Universal Replicator z/OS Operations |
