Rule Definition
When two CDS views refer to each other through a call, the result is a circular dependency. Neither CDS views can function without the other, and so neither is reusable without the other. This can cause unpredictable behaviors. Redesign May eliminate these dependencies to prevent problems during activation.

Remediation
If there are circular relationships among CDS VIEWS, the partitioning is not clear and should be redesigned.

Violation Code Sample

@AbapCatalog.sqlViewName: 'TEST1'
define view test_view1 as
       select from
       test_view2
       { * }
@AbapCatalog.sqlViewName: 'TEST2'
define view test_view2 as
          select from
          test_view1
          { * }
-----------------------------------
@AbapCatalog.sqlViewName: 'TEST1'
define view test_view1 as
       select from
       table1
       association to test_view2 as _assoc1
                      on table1.field =  _assoc1.field
       { _assoc1,
         field }

@AbapCatalog.sqlViewName: 'TEST2'
define view test_view2 as
       select from
       table2
       association to test_view3 as _assoc2
                      on table2.field =  _assoc2.field
       { _assoc2,
         field }

@AbapCatalog.sqlViewName: 'TEST3'
define view test_view3 as
       select from
       test_view1
       { _assoc1.field }

https://www.sap.com/documents/2019/01/0e6d5904-367d-0010-87a3-c30de2ffd8ff.html https://help.sap.com/doc/abapdocu_751_index_htm/7.51/en-us/abenddic_cds_cycle_problems.htm