SQL>
BEGIN
  DBMS_NETWORK_ACL_ADMIN.create_acl (
    acl          => 'user_sync.xml',
    description  => 'Purpose of the acl is user synchronization between XE database',
    principal    => 'USER_SYNC',
    is_grant     => TRUE,
    privilege    => 'connect',
    start_date   => SYSTIMESTAMP,
    end_date     => NULL);

  DBMS_NETWORK_ACL_ADMIN.assign_acl (
    acl         => 'user_sync.xml',
    host        => '127.0.0.1',
    lower_port  => 1,
    upper_port  => 9999);

  COMMIT;
END;
/

 *

ERROR at line 1:

ORA-30554: function-based index XDB.XDB$ACL_XIDX is disabled

ORA-06512: at "SYS.DBMS_NETWORK_ACL_ADMIN", line 252

ORA-06512: at line 2

Solution:

SQL>select owner, index_name, status, domidx_status, domidx_opstatus,funcidx_status from dba_indexes where domidx_opstatus is not null;

OWNER	INDEX_NAME	STATUS	DOMIDX_STATUS	DOMIDX_OPSTATUS	FUNCIDX_STATUS
XDB	XDBHI_IDX	VALID	VALID	VALID	ENABLED
XDB	XDB$ACL_XIDX	VALID	VALID	VALID	DISABLED

 

SQL>alter index XDB.XDB$ACL_XIDX rebuild;

Index altered.

SQL>select owner, index_name, status, domidx_status, domidx_opstatus,funcidx_status from dba_indexes where domidx_opstatus is not null;

OWNER	INDEX_NAME	STATUS	DOMIDX_STATUS	DOMIDX_OPSTATUS	FUNCIDX_STATUS
XDB	XDBHI_IDX	VALID	VALID	VALID	ENABLED
XDB	XDB$ACL_XIDX	VALID	VALID	VALID	ENABLED