Pythian Group

This post originated from a quick discussion we had internally on how to quickly and easily compare schemas between two Oracle databases. I learned about Sheeri Cabral’s post with a quick comparison solution for MySQL databases and I though of using a similar approach for Oracle. I did some testing and it worked quite well.

There certainly are tools in the market, free or not, that do this for us, and even generate scripts to correct differences. The steps below only go as far as to tell you what the differences are. However, they don’t require any additional tool and can be easily executed in any *nix or Windows environment.

The procedure uses the Oracle Data Pump utilities to extract one schema’s metadata and the Unix diff command to compare them. The metadata files generated by Data Pump, though, contain a lot of information about tables and indexes statistics that add too much noise to the diff output, since they usually differ a lot between databases. To eliminate that noise, I used the following small Perl script to pre-process the metadata files: Read the rest of this entry . . .

While perusing the Oracle 11g Data Pump documents recently, I noticed a new parameter that was introduced in Oracle 10g, but I had missed it there. The parameter is TABLE_EXISTS_ACTION, and it applies only to the Data Pump Import.

Basically, this feature allows you to decide how to handle importing data if a table already exists. The options are SKIP (defaut), APPEND, TRUNCATE, and REPLACE. Do these parameters look familiar? Possibly reminiscent of the SQL*Loader parameters (INTO TABLE x INSERT/REPLACE/TRUNCATE/APPEND)? They are very similar and they work the same way, with the exception of SKIP.

Here’s an explanation of each option.

• SKIP: The default value for TABLE_EXISTS_ACTION. If the table exists, then SKIP will cause the table (and any related data) to not be loaded. The table will be skipped.
• TRUNCATE: This will truncate the data in the table and load the data. If the table already exists, no metadata will be applied.
• APPEND: This will append the data to the end of the table. Again, if the table already exists, no metadata will be applied.
• REPLACE: This will drop the existing object, recreate the object with the information from the dumpfile, and then load the data.

Let’s create a simple test case to demonstrate. Read the rest of this entry . . .