insert into AAAJOB(PROCEDURENAME,DESCRIPTION) VALUES('OOO','PPP')
            *
ERROR at line 1:
ORA-06502: PL/SQL: numeric or value error: character string buffer too small
ORA-06512: at "PMSC0.AAAJOB_TIMING", line 10
ORA-04088: error during execution of trigger 'PMSC0.AAAJOB_TIMING'
===

CREATE TABLE PMSC0.AAAJOB
(
  CREATETS       TIMESTAMP(0)                   DEFAULT current_timestamp,
  PROCEDURENAME  VARCHAR2(100 CHAR),
  DESCRIPTION    VARCHAR2(100 CHAR),
  LASTUPDATEDBY  VARCHAR2(9 CHAR)
)
TABLESPACE PMSC0_DATA
PCTUSED    0
PCTFREE    10
INITRANS   1
MAXTRANS   255
STORAGE    (
            INITIAL          64K
            MINEXTENTS       1
            MAXEXTENTS       UNLIMITED
            PCTINCREASE      0
            BUFFER_POOL      DEFAULT
           )
LOGGING 
NOCOMPRESS 
NOCACHE
NOPARALLEL
MONITORING;


CREATE OR REPLACE TRIGGER PMSC0.AAAjob_timing
   BEFORE INSERT OR UPDATE
   ON PMSC0.AAAJOB    REFERENCING OLD AS old_row NEW AS new_row
   FOR EACH ROW
BEGIN
   IF    :new_row.createTS <> SYStimestamp
      OR :new_row.createTS IS NULL
   THEN
      SELECT current_timestamp
        INTO :new_row.createTS
        FROM DUAL;
   END IF;

   SELECT SYS_CONTEXT ( 'USERENV', 'OS_USER' )
     INTO :new_row.lastupdatedby
     FROM DUAL;
END;
/

      SELECT current_timestamp
        INTO :new_row.createTS

LASTUPDATEDBY  VARCHAR2(9 CHAR)

SQL> CREATE TABLE PMSC0.AAAJOB
  2  (
  3    CREATETS       TIMESTAMP(0)                   DEFAULT current_timestamp,
  4    PROCEDURENAME  VARCHAR2(100 CHAR),
  5    DESCRIPTION    VARCHAR2(100 CHAR),
  6    LASTUPDATEDBY  VARCHAR2(9 CHAR)
  7  )
  8  TABLESPACE PMSC0_DATA
  9  PCTUSED    0
 10  PCTFREE    10
 11  INITRANS   1
 12  MAXTRANS   255
 13  STORAGE    (
 14              INITIAL          64K
 15              MINEXTENTS       1
 16              MAXEXTENTS       UNLIMITED
 17              PCTINCREASE      0
 18              BUFFER_POOL      DEFAULT
 19             )
 20  LOGGING 
 21  NOCOMPRESS 
 22  NOCACHE
 23  NOPARALLEL
 24  MONITORING;
CREATE TABLE PMSC0.AAAJOB
*
ERROR at line 1:
ORA-01918: user 'PMSC0' does not exist

SQL> CREATE TABLE AAAJOB
  2  (
  3    CREATETS       TIMESTAMP(0)                   DEFAULT current_timestamp,
  4    PROCEDURENAME  VARCHAR2(100 CHAR),
  5    DESCRIPTION    VARCHAR2(100 CHAR),
  6    LASTUPDATEDBY  VARCHAR2(9 CHAR)
  7  )
  8  /

Table created.

SQL> CREATE OR REPLACE TRIGGER AAAjob_timing
  2     BEFORE INSERT OR UPDATE
  3     ON AAAJOB    REFERENCING OLD AS old_row NEW AS new_row
  4     FOR EACH ROW
  5  BEGIN
  6     IF    :new_row.createTS <> SYStimestamp
  7        OR :new_row.createTS IS NULL
  8     THEN
  9        SELECT current_timestamp
 10          INTO :new_row.createTS
 11          FROM DUAL;
 12     END IF;
 13  
 14     SELECT SYS_CONTEXT ( 'USERENV', 'OS_USER' )
 15       INTO :new_row.lastupdatedby
 16       FROM DUAL;
 17  END;
 18  /

Trigger created.

SQL> insert into AAAJOB(PROCEDURENAME,DESCRIPTION) VALUES('OOO','PPP');

1 row created.

select SYS_CONTEXT ( 'USERENV', 'OS_USER' ) from dual;