Here is how to create compressed Oracle export files on the fly even though the export utility does not support
writing to the Unix standard output stream. It is been tested on versions 7.3 though 8.1. It should also work on 9i, or any version of Oracle that runs on Unix.
Instead of piping the export file directly into the unix compress utility, create a named pipe with the mkfifo command and specify that as the name of the export file. Prior to starting the export, run a compress command in background that reads from the named pipe and writes to a regular file. That file will be created compressed on the fly.
To import from the compressed file to just the opposite. Create a named pipe and use zcat or uncompress in background to read from the compressed file and redirect the output to the named pipe. Then start the import utility and specify the named pipe as the import file.
This tip is useful because it allows you to created compressed export files directly without first having to run the export then compress the output file. To do it the traditional way requires enough disk space to hold both the compressed and uncompressed files simultaneously. My method bypasses the uncompressed file altogether.
To export to a compressed file:
mkfifo pipe.dmp compress < pipe.dmp > expdat.dmp.Z & exp user/passwd full=y file=pipe.dmpTo import the same file:
mkfifo pipe.dmp uncompress < expdat.dmp.Z > pipe.dmp & imp user/passwd full=y file=pipe.dmp
For More Information
- Feedback: E-mail the editor with your thoughts about this tip.
- More tips: Hundreds of free Oracle tips and scripts.
- Tip contest: Have an Oracle tip to offer your fellow DBAs and developers? The best tips submitted will receive a cool prize -- submit your tip today!
- Ask the Experts: Our SQL, database design, Oracle, SQL Server, DB2, metadata, and data warehousing gurus are waiting to answer your toughest questions.
- Forums: Ask your technical Oracle questions--or help out your peers by answering them--in our active forums.
- Best Web Links: Oracle tips, tutorials, and scripts from around the Web.