Why I cannot decrease the field size (table is full)

[Jörg Nowak]

Hello,

I try to decrease the size of one field in a table :

alter table tabelleA change checkS checkS tinyint(1); (it was tinyint(3) before).

ERROR 1114 (HY000): The table '#sql-1fc7_27' is full.

My database is 90 % full before I started this alter command (my table contains 1 million rows)..

My question: What happens during the alter command ? Does the database create some temporary tables before reducing the size of the table ?

That would be a disadvantage because small changes in database schema are not possible when the table contains many records.

I use MySQL Cluster 4.1.14

Joerg Nowak