Daily Archives: June 6, 2007

IMPORT & EXPORT from/to compressed files directly…

Well, a simple method to import(export) directly to(from) compressed files using pipes. Its for Unix based systems only, as I am not aware of any pipe type functionality in Windows. The biggest advantage is that you can save lots of space as uncompressing a file makes it almost 5 times or more. (Suppose you are uncompressing a file of 20 GB, it will make 100 GB) As a newbie I faced this problem, so thought about writing a post.

Lets talk about export first. The method used is that create a pipe, write to a pipe(ie the file in exp command is the pipe we created), side by side read the contents of pipe, compress (in the background) and redirect to a file. Here is the script that achieves this:

rm -f ?/myexport.pipe
mkfifo ?/myexport.pipe
cat ?/myexport.pipe |compress > ?/myexport.dmp.Z &
sleep 5
exp file=?/myexport.pipe full=Y log=myexport.log

Same way for import, we create a pipe, zcat from the dmp.Z file, redirect it to the pipe and then read from pipe:

rm -f ?/myimport.pipe
mkfifo ?/myimport.pipe
zcat ?/myexport.dmp.Z > ?/myimport.pipe &
sleep 5
imp file=myimport.pipe full=Y show=Y log=?/myimport.log

In case there is any issue with the script, do let me know 🙂

Update: If you are on Wintel, you can directly use a compressed folder as an export target. No need to create a pipe as the file system will automatically do it for you. ( Thanks Noons for the tip)

If you are using gunzip:

For export:

rm -f exp.pipe
mknod exp.pipe
gzip < exp.pipe > T1.dmp.gz &amp;amp;
exp file=exp.pipe full=Y log=myexport.log

For import:

rm -f imp.pipe
mknod imp.pipe
gzip < T1.dmp.gz > imp.pipe &amp;amp;
imp file=imp.pipe full=Y log=myimport.log

Update: I came across an article that discusses few ways to achieve the same on Windows. Check it here.