Within an IQ database, multiple read-only and read-write users can operate concurrently, as long as the writers are inserting data into (or deleting it from) different tables. So, for example, while User 1's transaction is inserting and deleting in the customer table, User 2 can begin a transaction that loads data into the employee table, as shown in Figure 10-3. At the same time other users can execute transactions that issue queries to both of these tables, or to any other tables in the database.
In general, read-only users connect to any query server or the write server, and read-write users connect to the write server. Read-write users may also connect to query servers, but can only modify:
Persistent objects in the query server’s local store
Global or local temporary tables
Figure 10-3: Concurrent insertions to different tables
Data definition operations on a single table lock out all other readers and writers from that table. See “Locks for DDL operations” for details.
