# When to Use Cached Table
+ TiDB limits the size of each cache table to 64 MB
+ `WORM` tables
+ Direct DDL operations on cached tables are not supported excepts **`ALTER TABLE {table_name} NOCACHE`**
+ For tables that are rarely updated, **`tidb_table_cache_lease`** should be increased to achieve better read performance

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`WORM` stands for "write once, read many" times.