Each TrueCopy for Mainframe volume pair consists of the P-VOL, which contains the original data, and the S-VOL, which contains the synchronous copy of the data on the P-VOL. After creating a copy pair, you can use the TrueCopy for Mainframe software to split, resynchronize, and reverse resynchronize pairs, and you can delete pairs as needed to return the volumes to an unpaired status.
- When paired, the volumes are synchronized.
- When split, new data is sent to the P-VOL but not the S-VOL.
- When resynchronized, data that changed while the pair was split is copied to the S-VOL.
- When necessary, data in the S-VOL can be copied to the P-VOL.
During normal operations, the P-VOL remains available to the host for read and write I/O operations. The secondary system rejects write I/Os for the S-VOL. The S-VOL can only be written to when the pair is split and when the write-enable option is specified for the S-VOL. In this instance, S-VOL and P-VOL track maps keep track of differential data and are used to resynchronize the pair.