Hi surya,
When you use group chart of accounts, then in gl master the field group chart of account become mandatory.
Suppose there are many company codes in the group and each one of them have their own operative chart of account. Then for consolidation purpose each of the gl of the individual company code need to be mapped to the group chart of accounts.
For ex. Say co code 0001 has expenses for telephone and co code 0002 has expenses head mobile expenses and both of them post this in their operative chart of accounts with diff. Gl no. And both have mapped their gl to the group coach which is communication expenses. Then at the GRP level in consolidation, just by checking communication gl, group can find out what is their communication expenses across all company codes.
Hope it clarifies.
Regards,
Kavita