Table Oracle PLSQL

SQL>
SQL> create table emp(
  2           emp_id                integer         primary key
  3          ,lastname               varchar2(20)    not null
  4          ,firstname              varchar2(15)    not null
  5          ,midinit                varchar2(1)
  6          ,street                 varchar2(30)
  7          ,city                   varchar2(20)
  8          ,state                  varchar2(2)
  9          ,zip                    varchar2(5)
 10          ,shortZipCode                   varchar2(4)
 11          ,area_code              varchar2(3)
 12          ,phone                  varchar2(8)
 13          ,company_name           varchar2(50));
Table created.
SQL>
SQL>
SQL> insert into emp(emp_id,lastname,firstname,midinit,street,city,state,zip,shortZipCode,area_code,phone,company_name)values
  2                      (1,'Jones','Joe','J','1 Ave','New York','NY','11202','1111','212', '221-4333','Big Company');
1 row created.
SQL> insert into emp(emp_id,lastname,firstname,midinit,street,city,state,zip,shortZipCode,area_code,phone,company_name)values
  2                      (2,'Smith','Sue','J','1 Street','New York','NY','11444','1111','212', '436-6773','Little Company');
1 row created.
SQL> insert into emp(emp_id,lastname,firstname,midinit,street,city,state,zip,shortZipCode,area_code,phone,company_name)values
  2                      (3,'X','Peggy','J','1 Drive','New York','NY','45502','2222','212', '234-4444','Medium Company');
1 row created.
SQL>
SQL>
SQL> create global temporary table working_emps
  2  on commit preserve rows
  3  as select * from emp;
SQL>
SQL> select *
  2  from working_emps;
    EMP_ID LASTNAME             FIRSTNAME       M STREET                         CITY                 ST ZIP   SHOR ARE PHONE    COMPANY_NAME
---------- -------------------- --------------- - ------------------------------ -------------------- -- ----- ---- --- -------- --------------------------------------------------
         1 Jones                Joe             J 1 Ave                          New York             NY 11202 1111 212 221-4333 Big Company
         2 Smith                Sue             J 1 Street                       New York             NY 11444 1111 212 436-6773 Little Company
         3 X                    Peggy           J 1 Drive                        New York             NY 45502 2222 212 234-4444 Medium Company
         1 Jones                Joe             J 1 Ave                          New York             NY 11202 1111 212 221-4333 Big Company
         2 Smith                Sue             J 1 Street                       New York             NY 11444 1111 212 436-6773 Little Company
         3 X                    Peggy           J 1 Drive                        New York             NY 45502 2222 212 234-4444 Medium Company
         1 Jones                Joe             J 1 Ave                          New York             NY 11202 1111 212 221-4333 Big Company
         2 Smith                Sue             J 1 Street                       New York             NY 11444 1111 212 436-6773 Little Company
         3 X                    Peggy           J 1 Drive                        New York             NY 45502 2222 212 234-4444 Medium Company
         1 Jones                Joe             J 1 Ave                          New York             NY 11202 1111 212 221-4333 Big Company
         2 Smith                Sue             J 1 Street                       New York             NY 11444 1111 212 436-6773 Little Company
         3 X                    Peggy           J 1 Drive                        New York             NY 45502 2222 212 234-4444 Medium Company
12 rows selected.
SQL>
SQL> select * from working_emps;
    EMP_ID LASTNAME             FIRSTNAME       M STREET                         CITY                 ST ZIP   SHOR ARE PHONE    COMPANY_NAME
---------- -------------------- --------------- - ------------------------------ -------------------- -- ----- ---- --- -------- --------------------------------------------------
         1 Jones                Joe             J 1 Ave                          New York             NY 11202 1111 212 221-4333 Big Company
         2 Smith                Sue             J 1 Street                       New York             NY 11444 1111 212 436-6773 Little Company
         3 X                    Peggy           J 1 Drive                        New York             NY 45502 2222 212 234-4444 Medium Company
         1 Jones                Joe             J 1 Ave                          New York             NY 11202 1111 212 221-4333 Big Company
         2 Smith                Sue             J 1 Street                       New York             NY 11444 1111 212 436-6773 Little Company
         3 X                    Peggy           J 1 Drive                        New York             NY 45502 2222 212 234-4444 Medium Company
         1 Jones                Joe             J 1 Ave                          New York             NY 11202 1111 212 221-4333 Big Company
         2 Smith                Sue             J 1 Street                       New York             NY 11444 1111 212 436-6773 Little Company
         3 X                    Peggy           J 1 Drive                        New York             NY 45502 2222 212 234-4444 Medium Company
         1 Jones                Joe             J 1 Ave                          New York             NY 11202 1111 212 221-4333 Big Company
         2 Smith                Sue             J 1 Street                       New York             NY 11444 1111 212 436-6773 Little Company
         3 X                    Peggy           J 1 Drive                        New York             NY 45502 2222 212 234-4444 Medium Company
12 rows selected.
SQL>
SQL> insert into working_emps
  2  select * from emp ;
3 rows created.
SQL>
SQL> drop table working_emps;
drop table working_emps
           *
ERROR at line 1:
ORA-14452: attempt to create, alter or drop an index on temporary table already in use
SQL> drop table emp;
Table dropped.
SQL>