When you try to open Costing Period and you get an error message

The period cannot be opened. (CST-2385103)  <br>**Cause** Number of open periods already reached maximum permissible of {MAX_OPEN_PERIODS}.  
**Action** Close the oldest open period or increase maximum number of open periods.

But you don't ready yet with the closing of previews periods.
the way of changing the Maximum allowed periods to be open in the same time is (quoted from Oracle Support):

1. Navigate to Setup And Maintenance

2. Find the Task list : Define Cost Accounting

3. Open the Task : `Manage Cost Accounting Periods'

4. Search for the Cost Organization in question.

5. In the Result, under Cost Books Tab Click Edit for the involved Cost Book.

6. in Edit Pop-up window, change Maximum Open Periods (increase the value)

7. Click Ok, then Save and Close.

8. Go back to Mange Cost Period and re-try to Open new Period.