A materialized view log is a schema object that records changes to a master table’s
data so that a materialized view defined on the master table can be refreshed
incrementally.

Each materialized view log is associated with a single master table. The materialized
view log resides in the same database and schema as its master table.

物化视图日志
1. 记录主表数据变化的方案对象 , 使得定义在主表上的物化视图能够增量刷新
2. 每个物化视图日志与一个主表相关 , 与主表位于同一数据库同一方案