Lock wait timeout exceeded when trying to alter a large table

Polyglot Projects Percona Toolkit
1

Hello,

When trying to alter a large table (~40gb) I get the error:
change line 10696.

This is the command I have executed pt-online-schema-change --alter “CHANGE colName colName DECIMAL( 14, 1 ) NULL DEFAULT NULL” D=dbName,t=tableName -uuser -ppasswordr --critical-load Threads_running=100 --execute

This table has many writes at all times and sometimes also many reads.

What should I do?

Thanks,
Guy