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.

• 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.