Sometime happened that I needed to export a database (either partially or ‘FULL’) not having enough disk free space available for all the operations: the export file by itself could barely fit into the few free disk space available so that I could not even think to compress it, because almost at the end of compression (gzip) the scenario would have been: export_file.dmp added to the almost 99.9% of the compressed export_file.dmp would exceed the free disk space available.
The following examples show how to do an export into a compressed file (gzip) in one single step avoiding wasted disk space.
momo@cujox:~ $ mkfifo fifo_dbexport_20081119.dmp
momo@cujox:~ $ nohup exp scott/tiger tables=(TABLE_1, TABLE_2, TABLE_3) FILE=fifo_dbexport_20081119.dmp LOG=dbexport_20081119.log &
momo@cujox:~ $ nohup gzip < fifo_dbexport_20081119.dmp > real_db_export_20081119.dmp.gz &
momo@cujox:~ $ rm fifo_dbexport_20081119.dmp
momo@cujox:~ $ mkfifo fifo_dbimport_20081119.dmp
momo@cujox:~ $ nohup gzip -d < real_db_export_20081119.dmp.gz > fifo_dbimport_20081119.dmp &
momo@cujox:~ $ nohup imp scott/tiger tables=(TABLE_1, TABLE_2, TABLE_3) IGNORE=Y FILE=fifo_dbimport_20081119.dmp LOG=dbimport_20081119.log &
momo@cujox:~ $ rm dbimport_20081119.dmp
