Open users in MDD

Hi

I Hav found some active users in my MDD database when i executed following command.

SQL> select username,account_status from dba_users;

USERNAME ACCOUNT_STATUS

-

-

SRMMDMCATALOG1_Z001 OPEN

SRMMDMCATALOG1_M001 OPEN

SRMMDMCATALOG1_Z000 OPEN

SRMMDMCATALOG1_M000 OPEN

SRMMDMCATALOG_Z000 OPEN

SRMMDMCATALOG_M000 OPEN

A2I_XCAT_DBS OPEN

MGMT_VIEW OPEN

MDM OPEN

I am not sure what are these users? ( I am aware of Admin, Master, USer1 etc.). And what is the role of these users in working of repository.

Regards