Final answer:
Cascade-cleanup of orphan-dependent CIs in a CMDB is recommended to ensure data consistency and minimize data redundancy, which indirectly leads to improved system performance due to a more streamlined database.
Step-by-step explanation:
The recommendation to apply cascade-cleanup operations to orphan-dependent Configuration Items (CIs) that existed in the CMDB before enabling the dependent CIs management feature is primarily due to two reasons: ensuring data consistency and minimizing data redundancy. Applying cascade-cleanup operations helps maintain the CMDB's accuracy by removing orphan CIs,
which no longer have a defined relationship or a relevant use in the database, effectively decluttering the CMDB and ensuring that data is consistent across the board.
Improved system performance is a natural byproduct of these efforts, because when redundant data or inaccurate configurations are eliminated, the system requires fewer resources to manage and query the CMDB. However, in the options provided, the focus on security might not be as direct and immediate as consistency and redundancy; therefore, enhanced overall system security isn't chosen as a primary reason.