There are four phases in a classic or offline table reorganization operation:
1. SORT - During this phase, if an index was specified on the REORG TABLE command, or a clustering index was defined on the table, the rows of the table are first sorted according to that index. If the INDEXSCAN option is specified, an index scan is used to sort the table; otherwise, a table scan sort is used. This phase applies only to a clustering table reorg operation. Space reclaiming reorg operations begin at the build phase.
2. BUILD - During this phase, a reorganized copy of the entire table is built, either in its table space or in a temporary table space that was specified on the REORG TABLE command.
3. REPLACE - During this phase, the original table object is replaced by a copy from the temporary table space, or a pointer is created to the newly built object within the table space of the table that is being reorganized.
4. RECREATE ALL INDEXES - During this phase, all indexes that were defined on the table are recreated