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 Oracle Environment Variable Settings
Oracle Tips by Burleson Consulting

Advanced Oracle Utilities: The Definitive Reference by Rampant TechPress is written by the top Oracle database experts (Bert Scalzo, Donald Burleson, and Steve Callan).  The following is an excerpt from the book.

Environment variable settings

Each environment variable line consists of a variable name, an equal sign (=), and a value.  Values that contain spaces need to be enclosed within quotes.  The following are some examples of environment variable settings:


color = red

ORACLE_HOME = /u01/app/oracle/product/10.2.0/db_1
title = ‘My Life in a Nutshell’


As with the operating system itself, variable names in the crontab are case-sensitive and system variables are usually defined with upper case names, while user defined variables are defined with lower case names.

Crontab command Lines

Each crontab command line is comprised of six positional fields specifying the time, date and shell script or command to be run.  The format of the crontab command line is described in Table 4.2:



Valid values





Day of Month




Day of Week



Command path/command

Table 4.2:  Crontab Command Line Format


In all fields which take numeric values, a single number, a range of numbers indicated with a hyphen (such as 2-4), a list of specific values separated by commas (like 2,3,4) or a combination of these designations separated by commas (such as 1,3-5) are allowed.  Also allowed is an asterisk (*) indicating every possible value of this field.  All conditions must be met for the entry to execute.  This can all get rather confusing so make sure that one understands exactly what an entry is doing before making any changes to it.


This entry will run the script cleanup.ksh at 0 minutes past the hour, 6 am, every Monday.  This illustrates that for a crontab to execute, all of the conditions specified must be met. So even though every day of the month has been said by making the third field a wildcard, the day also has to meet the final condition that the day is a Monday.


# Run the Weekly Management Report every Monday at 7:00 AM
# and save a copy of the report in my /home directory
00 07 * * 1 /home/bei/scripts/weekly_mgmt_rpt.ksh wprd > /home/terry/weekly_mgmt_rpt.lst


This entry is similar to the previous entry, but will execute at 7:00am.  Since the hour is in 24 hour format (midnight is actually represented as 00), the 07 represents 7:00 a.m.  This entry again will only be run on Mondays.


# Lunch Time Notification - run Monday-Friday at Noon -
# sends a message to all users indicating it's lunch time
00 12 * * 1-5 /home/terry/lunch_time.ksh wprd > /tmp/lunch_time.lst


This lunch reminder is set up to run at 12:00 p.m. Monday through Friday only.


The most important thing to remember is that a crontab entry will execute every time all of its conditions are met.  To take the last entry as an example, anytime it is 00 minutes past the hour of 12 on any day of the month and any month of the year and the day of the week is between Monday and Friday inclusive (1-5), this crontab will be executed.


Most crontab entries will have some wildcards, but be careful where they are used.  For instance, if a * was mistakenly placed in the minute position of the last crontab example above, the script would end up running for ever minute of the 12:00 hour instead of just once at the beginning of the hour.  Remember that the wildcard means all, not 'any'.

The day-of-week field accepts either zero or seven as a value for Sunday.  Any of the time/date fields can also contain an asterisk (*) indicating the entire range of values.  Additionally, month and day-of-week fields can contain name values, consisting of the first three letters of the month, as indicated in Table 4.3.



Valid Entries (case insensitive)

Days of the week

sun, mon, tue, wed, thu, fri, sat



Months of year

jan, feb, mar, apr, may, jun, jul, aug, sep, oct, nov, dec



Table 4.3:  Month and Day-of-week Fields

When numbers are used, the user can specify a range of values separated by a hyphen or a list of values separated by commas.  In other words, specifying 2-5 in the hour field means 2AM, 3AM, 4AM and 5AM, while specifying 2,5 means only 2AM and 5AM.


Most people will execute shell scripts from the crontab, but any operating system command can be executed. If the command or script called in the crontab typically sends output to the screen, the move may be to redirect that output to a log file with the >> symbol so it can be checked later.  The > redirection symbol will create a new file, while the >> symbol will append to an existing file, or create a new one if it does not exist.  Generally, a new log file will be created with each execution, and the log file will be periodically reviewed for problems.


By default, the output from a job is emailed to the owner of the job or the user specified by the mailto variable.  If this is unacceptable, the output can be redirected in a number of ways, including:


# Mail the output of the job to another user.

command | mail -s "Subject: Output of job" user


# Standard output redirected to a file.

command >> file.log


# Standard output and standard error redirected to a file.

command >> logfile 2>&1


# Throw all the output away

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r more details on Oracle utilities, see the book "Advanced Oracle Utilities" by Bert Scalzo, Donald K. Burleson, and Steve Callan.

You can buy it direct from the publisher for 30% off directly from Rampant TechPress.



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