Oracle: logon trigger

CREATE TABLE logonaudittable (
event VARCHAR2(10),
sid NUMBER,
serial# NUMBER,
TIMESTAMP DATE,
username VARCHAR2(30),
osuserid VARCHAR2(30),
machinename VARCHAR2(64)
);

CREATE OR REPLACE TRIGGER logon_trg
AFTER LOGON ON DATABASE
DECLARE machinename VARCHAR2(64);
 osuserid VARCHAR2(30);
 v_sid NUMBER(10);
 v_serial NUMBER(10);
CURSOR c1 IS
 SELECT sid, serial#, osuser, machine FROM v$session v
 WHERE v.sid = (SELECT sid FROM gv$mystat WHERE ROWNUM = 1 ) ;
BEGIN
OPEN c1;
FETCH c1 INTO v_sid, v_serial, osuserid, machinename;
INSERT INTO logonaudittable VALUES ( 'LOGON',
 v_sid, v_serial,
 SYSDATE, USER, osuserid, machinename );
CLOSE c1;
END;

CREATE OR REPLACE TRIGGER logoff_trg
BEFORE LOGOFF ON DATABASE
DECLARE machinename VARCHAR2(64);
osuserid VARCHAR2(30);
v_sid NUMBER(10);
v_serial NUMBER(10);
CURSOR c1 IS
 SELECT sid, serial#, osuser, machine FROM v$session v
 WHERE v.sid = (SELECT sid FROM gv$mystat WHERE ROWNUM = 1 ) ;
BEGIN
OPEN c1;
FETCH c1 INTO v_sid, v_serial, osuserid, machinename;
INSERT INTO logonaudittable VALUES ( 'LOGOFF', v_sid, v_serial, SYSDATE, USER, osuserid, machinename );    
CLOSE c1;
END;