In some situation when you want to re-index Magento catalog you will get an error message or reindex process will be broken. This problem is appearing when you have a lot of products in database and limited server resource. You can try to reindex from command line or shell.
In Magento there is folder with name “shell” in this folder you will find file with name “indexer.php” this is shell script for reindexing. You will ask yourself how to call this script, and take a look on my examples below and everything will be clear.