Maintain the Material Master company code in OMSY.

This is done when you want :

1.  To create a material master record, the control record must exist for the company code 
     for which you want to create your master record.

2.  To set up a company code, enter the current period here. 

3.  When changing the Allow backposting or Disallow backposting indicators 
 

You can also use MMRV to set the Allow/Disallowed backposting indicators.

The current and previous period is shown on both transaction codes.

MM Related:

• Automate the opening of MM periods
• Re-Open The Previous Period
• Movement Error - Posting Only Possible Between

SAP Materials Management Tips
SAP MM Configuration Tips and Materials Management

Best regards,
SAP Basis, ABAP Programming and Other IMG Stuff
http://www.erpgreat.com