Who can resolve the error PLS-00201: identifier ... must be declared?

To use DBMS_ALERT, you must have been explicity granted execute priviliges by sys.

SQL> CONN REPOS_OWNER/REPOS_OWNER@DESIGNER
Connected.
SQL>
SQL> DESC DBMS_ALERT
ERROR:
ORA-04043: object "SYS"."DBMS_ALERT" does not exist
 
 
SQL> conn sys@designer as sysdba
Enter password:
Connected.
SQL>
SQL> grant execute on dbms_alert to public;
 
Grant succeeded.
 
SQL> CONN REPOS_OWNER/REPOS_OWNER@DESIGNER
Connected.
SQL>
SQL> desc DBMS_ALERT
PROCEDURE REGISTER
 Argument Name                  Type                    In/Out Default?
 ------------------------------ ----------------------- ------ --------
 NAME                           VARCHAR2                IN
PROCEDURE REMOVE
 Argument Name                  Type                    In/Out Default?
 ------------------------------ ----------------------- ------ --------
 NAME                           VARCHAR2                IN
PROCEDURE REMOVEALL
PROCEDURE SET_DEFAULTS
 Argument Name                  Type                    In/Out Default?
 ------------------------------ ----------------------- ------ --------
 SENSITIVITY                    NUMBER                  IN
PROCEDURE SIGNAL
 Argument Name                  Type                    In/Out Default?
 ------------------------------ ----------------------- ------ --------
 NAME                           VARCHAR2                IN
 MESSAGE                        VARCHAR2                IN
PROCEDURE WAITANY
 Argument Name                  Type                    In/Out Default?
 ------------------------------ ----------------------- ------ --------
 NAME                           VARCHAR2                OUT
 MESSAGE                        VARCHAR2                OUT
 STATUS                         NUMBER(38)              OUT
 TIMEOUT                        NUMBER                  IN     DEFAULT
PROCEDURE WAITONE
 Argument Name                  Type                    In/Out Default?
 ------------------------------ ----------------------- ------ --------
 NAME                           VARCHAR2                IN
 MESSAGE                        VARCHAR2                OUT
 STATUS                         NUMBER(38)              OUT
 TIMEOUT                        NUMBER                  IN     DEFAULT
 
SQL>