Watching SQL Execute on Oracle – Part I

Do you have SQL running within your database? Of course you do.
This article is the first in a series to introduce you to a method of finding information
about the SQL your users are executing in your databases.

Your ability as a DBA to detect who is accessing the
database and the SQL they are executing is paramount in your ability to
properly manage and give feedback on the type of work your database is
requested to do. This article will begin our series with an introduction to
determining who is logged into your database and what SQL they are executing.
This article is not concerning itself with the tuning of SQL but rather a
primer so that you can get familiar with or re-acquainted with the underlying
tables within Oracle that give information on who and what is being done around
the SQL.

V$SESSION

The V$SESSION is often the jumping off place
to determine who is logged into the database and a high level overview of what
they are doing. In Table 1 I have given a subset of the columns
this view contains. While there are other columns in this view that relate to
operating system information and the application being executed, I am only
presenting those columns that give us the basis for our jumping off point to
determine that this is in fact an active user and also the columns we will need
later to join to the actual SQL being executed.

Table 1.

Limited V$SESSION
information

In order to extract the information, you can issue a SQL
statement such as the following in Listing 1. This is a very simplistic
statement but gives us all the information we need to determine if the user is
actually executing SQL at the time. If a user has SQL that is executing, the
status column will be ACTIVE and the SQL_ADDR & SQL_HASH_VALUE will be
populated. I have given the output of two different executions of this
particular SQL against the V$SESSION view. The first shows where a user was
noticed logged into our database but is basically inactive and there is no SQL
address or hash value. The second execution of this SQL shows a user who is
actively executing SQL, denoted by the values in the address and hash value
columns.

Listing 1.

Extracting simplistic columns to show sessions that are
executing SQL

select sid,
       to_char(logon_time,’MMDDYYYY:HH24:MI’) logon_time,
       username,
       type,
       status,
       process,
       sql_address,
       sql_hash_value
  from v$session
where username is not null
Inactive session with no SQL executing
SID LOGON_TIME      USERNAME  TYPE STATUS   PROCESS      SQL_ADDR SQL_HASH_VALUE
—- ————– ——— —- ——– ———— ——– ————–
 150 06252004:06:23 JKOOPMANN USER INACTIVE 3528:3036    00                    0
Active session with SQL executing
SID LOGON_TIME      USERNAME  TYPE STATUS   PROCESS      SQL_ADDR SQL_HASH_VALUE
—- ————– ——— —- ——– ———— ——– ————–
 150 06252004:06:23 JKOOPMANN USER ACTIVE   3528:3036    6879D780     2803425422