Engineering Change Management for BOM Changes 
You use engineering change management to change BOMs with history. You make changes with history by referring to a change master record.
A change with history has the following distinguishing features:
- In the standard R/3 System, the change comes into effect on a specific date.
If the change master record has an effectivity type, the change comes into effect when certain parameters apply (for example, range of serial numbers).
- The changed object is stored twice: in its pre-change state and in its post-change state.
The pre-change state of the object ends on the valid-to date. The post-change state of the object starts on the valid-from date. - Changes are documented in a change master.
- You can use an engineering change request (ECR) to control the change process. An ECR is converted to an engineering change order (ECO).
- You can assign a revision level to certain change statuses (versions) of a material or document.
- If your change is subject to special security requirements, you can use digital signatures to make additional authorization checks.