Posts Tagged ‘SQL statement’

Have you needed to find out what SQL was running in the database? Much of my time is spent on out data warehouse where long expensive queries may be running. When someone calls to ask why things are running slow one area to look is what SQL are they running. The database may not be running slow, but their SQL is.

When Oracle executes a query, it places it in memory. This allows Oracle to reuse the same SQL if needed by the executing session at a later date or by another user that may need the same SQL statement. Oracle assigns a unique SQL_HASH_VALUE and SQL_ADDRESS to each SQL statement. By Oracle doing this, it provides us a method to determine who is executing what SQL based on the join columns from the V$SESSION of SQL_ADDRESS & SQL_HASH_VALUE to the V$SQLAREA view and columns ADDRESS and HASH_VALUE.

Here is a small script to determine what SQL is currently executing.

select sesion.sid,
  from v$sqlarea sqlarea, v$session sesion
 where sesion.sql_hash_value = sqlarea.hash_value
   and sesion.sql_address    = sqlarea.address
   and sesion.username is not null 


Often you may have an active session and actually show a valid SQL statement through the V$SESSION and V$SQLAREA views that seems to be taking very long. Users may be complaining that their query is “stuck” or not responsive. You as a DBA can validate that the SQL they are executing is actually doing something in the database and not “stuck” be simply querying the V$SESS_IO view to determine if the query is in fact “stuck” or is actually doing work within the database. Granted, this does not mean there isn’t a tuning opportunity but you can at least show the SQL is working.

Here you can see the I/O being done by an active SQL statement.

select sess_io.sid,
  from v$sess_io sess_io, v$session sesion
 where sesion.sid = sess_io.sid
   and sesion.username is not null 


If by chance the query shown earlier in the V$SQLAREA view did not show your full SQL text because it was larger than 1000 characters, this V$SQLTEXT view should be queried to extract the full SQL. It is a piece by piece of 64 characters by line, that needs to be ordered by the column PIECE.

Here is the SQL to show the full SQL executing for active sessions.

select sesion.sid,
  from v$sqltext sqltext, v$session sesion
 where sesion.sql_hash_value = sqltext.hash_value
   and sesion.sql_address    = sqltext.address
   and sesion.username is not null
 order by sqltext.piece 


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