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In this example, all of the output will be sent to /dev/null, whether it is standard output generated by the script or error output generated by the shell or the commands in the script. This kind of cron job is usually created because a simple cron entry without any redirection will cause an e-mail containing all the output, both standard output and error output, to be sent to the job s owner. Many users don t want this type of annoying e-mail, but instead of modifying the script to output information only when useful, they set up the cron job to throw all of it out. This is a bad habit to develop. I have seen jobs like this run for years under the assumption that they were performing the desired tasks, when all the while they did nothing because they were broken and the error output was never sent to alert users of the problem. As in the previous cron example, users will sometimes attempt to remove the output with syntax like this:

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Suppose the transaction data in the previous example were not evenly distributed among the quarters. What if, due to business and cyclical reasons, an overwhelming number of sales occurred in the last two quarters, with the earlier quarters contributing relatively negligible sales Range partitioning will be good only in theory, because the last two quarters could end up each having almost half of the original nonpartitioned table s data. In such cases, it s better to use the hash-partitioning scheme. All you have to do is decide on the number of partitions, and Oracle s hashing algorithms will assign a hash value to each row s partitioning key and place it in the appropriate partition. You don t have to know anything about the distribution of the data in the table, other than that the data doesn t fall into some easily determined ranges. All you need to do is provide a partition key, which in the hash-partitioning scheme shown next is the ticket_no column:

The HOST command enables you to use operating system commands from within SQL*Plus. You may, for example, want to see if a file exists in a certain directory, or you may want to use the cp or tar commands at the UNIX level and return to your SQL*Plus session to resume interacting with the Oracle database. Here is an example showing how to use the HOST command: SQL> HOST cp /u01/app/oracle/new.sql /tmp

Thunks generated for P/Invoke functions can be grouped into three performance categories as follows: Inlined thunks: As you can conclude from the name, the native code of an inlined thunk is inlined into the caller s code This saves the costs of calling a thunk function explicitly, and it allows the JIT compiler and the processor to further optimize code execution Therefore, inlined thunks are the fastest ones..

The HOST command in the preceding example will help you copy the new.sql file from the specified directory to the tmp directory. Just about any command you can use at the operating system level can be executed using the HOST command. You can replace the HOST command with ! (bang, or exclamation point) to run operating system commands from within SQL*Plus, as in the following example: SQL> ! cp /u01/app/oracle/new.sql /tmp

If you just type the command by itself, as in HOST or !, you ll be transported to the operating system directory from which you logged in to the SQL*Plus session.

Even assuming that we do want to suppress all output, this syntax is wrong for the intended purpose. You ll notice that the > /dev/null and 2>&1 pieces of the entry are reversed. In its current form, stderr output from the job will continue to be mailed to the user.

When you re done with your operating system task, just type exit on the command line and you ll return to the SQL*Plus session you just left. Here s an example: SQL> HOST $ exit SQL>

The SPOOL command enables you to save the output of one or more SQL statements to an operating system file in both UNIX and Windows: SQL> SQL> SQL> SQL> SET LINESIZE 180 SPOOL employee.lst SELECT emp_id, last_name, salary, manager FROM employee; SPOOL OFF;