OSS Note 912620 를 보니 흥미로운게 있네요.

보통 인덱스 태우기 위해선 순서대로 인덱스 필드를 만들어 줘야 타는 걸로 알고 있어서

Second 인덱스 생성시 MANDT를 반드시 추가해왔는데 대부분 그럴 필요가 없네요. 

16. Should indexes always begin with the client column?

              For historical reasons, many SAP indexes begin with the client column (MANDT, CLIENT, MANDANT, ...). In many cases, this column only increases overhead by increasing the size of the index. The client column is only useful or advantageous in a limited number of situations:

• There are selections that can be completely covered by the index if the index includes the client, which makes a processing-intensive table search unnecessary.

• The client is used in a unique index to guarantee application consistency.

• A short-term work-around is required for the CBO (Cost-Based Optimizer) problem described in Note 176754 (18).

• The table contains several filled clients. Therefore, the client condition is selective in this context.

              In most cases, it is not necessary to include the client in the index.