SR 4 DB

What are  parallel  sessions ? select qcsid , count( 1 ) from v$px_session group by qcsid ; QCSID field means Query Coordinator, main session that coordinates slave sessions. Details....  COL USERNAME FOR A16 HEADING 'Username' COL MACHINE FOR A24 HEADING 'Machine' COL PROGRAM FOR A33 HEADING 'Program' COL OSUSER FOR A14 HEADING 'OS | User' COL QC FOR A3 ALTER SESSION SET NLS_DATE_FORMAT= 'DD-MON-YYYY HH24:MI:SS' ; SET LIN 150 SET PAGES 103 compute sum LABEL 'Total Memory'     of memory_mb on report compute count LABEL 'Count Parallel' of sid on report undefine SID break on report select s .sid,decode( pxs .sid, pxs . qcsid , 'X' ,NULL) QC ,   s . username , s . osuser , p. spid "OS PID" , s .program, s . machine , status , s . logon_time ,round(p. PGA_ALLOC_MEM / 1024 / 1024 ) memory_mb from v$session s , v$process p, v$px_

SQL> create table hr . numbers (id number ) tablespace EXAMPLE ; Table created . SQL> insert into hr . numbers (id) values( 19 ); SQL>   insert into hr . numbers (id) values( 3 ); SQL>   insert into hr . numbers (id) values( 15 ); SQL> insert into hr . numbers (id) values( 9 ); SQL>   insert into hr . numbers (id) values( 21 ); SQL>   insert into hr . numbers (id) values( 7 ); SQL>   insert into hr . numbers (id) values( 17 ); SQL>   insert into hr . numbers (id) values( 1 ); SQL> insert into hr . numbers (id) values( 11 ); SQL>   insert into hr . numbers (id) values( 5 ); SQL> commit; Commit complete. SQL> select id from hr . numbers ;         ID ----------         19          3         15          9         21          7         17          1         11          5 10 rows selected . Common Mistake.   A common mistake is  we