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Error Conditions for Online DDL

Here are the primary reasons why an Online DDL operation could fail:

•    If a LOCK clause specifies a Iow degree of locking (shared or nonę) that is not compatible with the

particular type of DDL operation.

•    If a timeout occurs while waiting to get an exclusive lock on the table, which is needed briefly during

the initial and finał phases of the DDL operation.

•    If the tmpdir [571] file system runs out of disk space, while MySQL writes temporary sort files on

disk during index creation.

•    If the alter table takes so long, and concurrent DML modifies the table

so much, that the size of the temporary Online long exceeds the value of the