The reorg command can improve performance for data-only-locked tables by improving the space utilization for tables and indexes. The reorg subcommands and their uses are:
reclaim_space – cears committed deletes and space left when updates shorten the length of data rows.
forwarded_rows – returns forwarded rows to home pages.
compact – performs both of the operations above.
rebuild – rebuilds an entire table or index.
When you run reorg rebuild on a table, it locks the table for the entire time it takes to rebuild the table and its indexes. This means that you should schedule the reorg rebuild command on a table when users do not need access to the table.
All of the other reorg commands, including reorg rebuild on an index, lock a small number of pages at a time, and use short, independent transactions to perform their work. You can run these commands at any time. The only negative effects might be on systems that are very I/O bound.
For more information on running reorg commands, see the System Administration Guide.