• Locking--During the modify procedure, the table is exclusively locked and inaccessible to other users.

• Secondary Indexes--Secondary indexes are destroyed when you modify the base table storage structure. Modifying Secondary Indexes provides more information.

• Disk Space--When a table storage structure is modified, temporary sort files are created. Before the old table can be deleted, a new table must be built. Once it is completely built, the old table is deleted, and the temporary file is renamed with the old table name. Space Requirements for Modify Operations provides more information.

• Partitioned tables--Modifying a table with a large number of partitions requires a large amount of space in the transaction log file. It is possible to fill the log file with a modify of a partitioned table.