Best way to minimize the index rebuild time
Problem Statement :
1. Customer is performing monthly once ( weekends on maintenance window ) purging one month's data and rebuild the related indexes.
2. An integration program/application that runs 24/7 that cannot acquire a lock to perform index rebuild activity. Took the outage and performing the rebuild and it is taking more time.
Oracle database is running in 11g version.
Please suggest with your recommendations.