Differential data is managed by the bitmap in units of tracks. A track that receives a write command while the pair is split is managed as differential data in the bitmap. When the pair is resynchronized, the differential data is copied to the S-VOL in units of tracks.
When a GAD pair contains a DP-VOL that is larger than 4,194,304 MB (8,589,934,592 blocks), the differential data is managed by the pool to which the GAD pair volume is related.
In this case, additional effective pool capacity (up to 4 pages, depending on the software configuration) is required for each increase of user data size by 4,123,168,604,160 bytes (~4 TB). For a GAD pair with a DP-VOL that is larger than 4,194,304 MB (8,589,934,592 blocks), data management might fail due to insufficient effective pool capacity. If this occurs, all of the P-VOL data (all tracks) is copied to the S-VOL when the pair is resynchronized.
For instructions on releasing the differential data (pages) managed in a pool, see Releasing the differential data managed in a pool.