Problem One :
Does anyone knows where I can track who has made any changes in the configuration?

Problem Two :
Also, recently I was asked if those data can be deleted from ACCT* tables. Also, he commented there was a high increase in usage for these ACCT* tables that are related to MM. We have set up 2 phases in my company but this sudden increase in usage only happens in phase 2.  Does anybody know what do these tables contain? Are there some settings that were made by the consultant in the configurations?

For :
1. - go to spro- then select any configuration tcode then menu-utilities-change log (provided the Change Log Tables is turn on by your Basis team. Usually this is turn off.  To turn it on, you can refer to IMG - Basis Components - System Administration - Tables Changes Recording).

2.  Please refer to OSS Note: 48009 - Tables ACCTHD, ACCTIT, ACCTCR: Questions and answers for the complete detail of ACCT* tables, when you post goods movement and invoice receipt, the FI/CO interface is documented in the forms of document in the tables ACCT*.

Defining Storage Location 
One Storage Location for Two Different Plant

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