SAP MM 预留单据的历史修改记录？
在笔者眼里，SAP系统是一个高度严谨的软件系统。用户在SAP系统里的相关操作，系统都会做记录。用户对于系统的相关单据的增删改，SAP系统都有保留change history,并且可以很方便被人查询这些change history。但是笔者发现，并不是所有单据的修改，SAP系统都提供很好的查询change history的方式，比如Reservation单据。
如下的预留单ITEM，笔者有将数量由80改成了81，
笔者试图找到该预留单据的change history, 如同查询其它单据修改记录的方式，找遍了MB23事务代码里的诸多菜单，都找不到。
上网查资料，发现SAP标准系统是不保留预留单据的change history信息的。看来SAP保持增删改的痕迹以方便后续追溯的严谨风格，执行的并不彻底！当然SAP系统对于任何单据的修改都有记录在表CDHDR & CDPOS里，但是标准系统里，这2个表里的数据，对于业务用户，并不能方便的查询。
SAP NOTE 1927840 供参考。
1927840 - Change log for reservations
Symptom
Create a Purchase Requisition with reference to a reservation and later make changes to delivery date,for example, in transaction ME52N. The field RESB-BDTER is updated with the delivery date changes but no change log is written.
You would like to record changes made to reservations.
Reproducing the Issue
Call a reservation in transaction MB22.
Make a change to the reservation.
Save the changes.
There is no change log.
Cause
This is standard SAP system design.
Resolution
In enhancement MBCF0007 you find user exit EXIT_SAPMM07R_001.
This user exit is called directly after the COMMIT WORK statement in MB21/MB22 and contains information related to the old and new item details in table RESB. You could use this user exit to update the reservation changes to a custom table.
The standard change log table are CDHDR & CDPOS. If you were to use these as part of a custom development to capture reservation changes you would have to pay special attention to performance as these tables are often very large.
