Users get the ORA-01502 error when attempting to login to E-Notebook:

Error Changing Root
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Sorry, while getting data for notifications of section "Home Page" of user "xyz": an error occurred while executing a database operation: ORA-01502: index 'ENDB.ENI_PROPERTY_VALUES_2' or partition of such index is in unusable state.

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Solution:

The DBA found the index was in unusable state in the database using the below sql:

SQL> select index_name, status from dba_indexes where status ='UNUSABLE' and index_name='ENI_PROPERTY_VALUES_2';

And by rebuilding the index, the issue was fixed.

Tested in E-Notebook Version 17.1.1