The following conditional expression can be used to estimate the maximum number of pairs that can be migrated concurrently:
Σ(α) ≤ (β) and Σ(γ) ≤ (δ)
- Σ (α) = total number of differential tables needed for migrating all volumes
- (β) = total number of differential tables available in the storage system
- Σ (γ) = total number of pair tables needed for migrating all volumes
- (δ) = total number of pair tables available in the storage system
As calculated in Calculating the required amount of differential tables for open-systems volumes, the number of differential tables required for each migration pair is 577, and the number of required pair tables for each migration pair is 17. If you want to create 20 migration pairs, 60 differential tables and 20 pair tables are required. These numbers are entered into the original equation:
[ (577 × 20) = 11,540 ] ≤ 26,176 and [ (17 × 20) = 340 ] ≤ 8,192
Because this expression is true, you can create all 20 pairs.
In the preceding calculation, it is assumed that only Volume Migration is running. However, differential tables are resources that are also shared by ShadowImage , ShadowImage for Mainframe, and Compatible FlashCopy® V2. The total number of pair tables used by ShadowImage , ShadowImage for Mainframe, Compatible FlashCopy® V2, and Volume Migration must be within the value of (β) and (δ). For details on calculating the number of differential tables and pair tables used by these other software products, see the documentation for the software products.