Before diving into the official documentation, take a look at the following SAP Notes:
- SAP note 2187353 - SP Equivalence for update/upgrade to SAP NW 7.5
- SAP note 2204286 - Deprecated Features in SAP Enterprise Portal
- SAP note 2206460 - Release restrictions for SAP NetWeaver 7.5
- SAP note 2031108 - SAP Fiori Integration with SAP Enterprise Portal - Central note
- SAP note 2261419 - Maintenance Strategy for FLP on Portal
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Explore the Performance guidelines:
(Those guidelines are relevant also for EP 7.5)
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Have any custom Portal applications developed? Take a look at the following blogs:
(Those blogs are relevant also for EP 7.5)
- How To Migrate Custom Portal Applications to SAP NetWeaver 7.3
- Locating Relevant JAR Files When Migrating Custom Applications to SAP NetWeaver Portal 7.3
- Customizing Logon Page on Portal 7.3
For Custom Web Dynpro Java applications read the following documentation: - Migrating Web Dynpro Applications
- Migrating Web Dynpro Application Projects from SAP NetWeaver 7.0 to Higher Version
- Running the Application Projects' Migration Wizard