If a table is an in-memory table (M-table), the entire contents of the table are stored in memory so that the data can be accessed as quickly as possible. If a table is disk-based (D-table), the data is stored primarily on disk, and usually the server copies only small pieces of data at a time into memory.
From application design perspective, in-memory tables and disk-based tables are the same in most respects.
▪Both table types provide full persistence of data unless specified differently.
▪You can run the same types of queries on each of them.
▪You can combine disk-based and in-memory tables in the same SQL query or transaction.
▪Both table types can be used with indexes, triggers, stored procedures, and other common database objects.
▪Both table types allow constraints, including primary key and foreign key constraints, although there are some limitations on foreign key constraints with non-persistent in-memory tables.
The main difference between M-tables and D-tables is performance. M-tables provide better performance; they can provide the same durability and recoverability as D-tables. For example, read operations on M-tables do not wait for disk access, even when the system is engaged in activities such as checkpointing and transaction logging.
With solidDB®, you can decide which tables are in-memory tables and which tables are disk-based tables. For example, you can put heavily used tables in main memory so that they can be accessed more quickly. If you have enough memory, you can put all of your tables in main memory.