Pros
1. Works very well if the application has isolated functional parts.
2. Works well together with a parallel extension of existing functionality using .NET.
3. No interoperability overhead between migrated ASP and COM components through all the layers.
4. No conversion between complex data types, like dataset and recordset is needed.
5. Usually less risky, compared with complete layer horizontal migration.
6. Vertically migrated application part can be redesigned and take advantage of .NET benefits through all migrated layers.
Cons
1. Interoperability overhead to communicate with the rest of the nonmigrated unmanaged code.
2. Additional effort to refactor independent functionality for vertical migration.
3. Migrated shared code has to be accessed through interoperability or duplicated.
4. State synchronization is still needed.
5. Security for a mixed environment has to be addressed.
6. Deployment should be done for the mixed environment.

Table 9: Pros and cons of vertical migration.

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