Web templates from SAP BW 3.x and SAP NetWeaver 7.2 are stored in separate tables. You can edit Web templates from SAP BW 3.x with the BEx Web Application Designer from SAP BW 3.x. This is still available in SAP NetWeaver 7.2.
To help you convert Web templates of SAP NetWeaver BW.3x format to Web templates of SAP NetWeaver 7.2 format and thus migrate them, the migration tool for the BEx Web Application Designer from SAP NetWeaver 7.2 is provided.
The migrated Web templates can then be edited with the Web Application Designer from SAP NetWeaver 7.2 only. Since there are two independent versions of the Web Templates, you can continue to use Web templates from SAP BW 3.x in the BEx Web Application Designer from SAP BW 3.x even after the migration.
General Practices with Migration
If you want to migrate Web templates with SAP NetWeaver BW.3x format to SAP NetWeaver 7.2, open the SAP NetWeaver 7.2 BEx Web Application Designer and use the migration tool provided in the Tools menu. As soon as you have migrated a Web template from SAP BW 3.x, you can then use it with the BEx Web Application Designer from SAP NetWeaver 7.2.
Since Web templates of SAP BW 3.x format are neither overwritten nor changed during migration, you can migrate Web templates with this format as often as you want to adapt them to your needs.
Note that under certain circumstances, you may have to edit the Web template to adjust it to your requirements before saving it.