When certain transactions need only to read the database, declaring those transactions as read-only minimizes contention with read/write transactions. Transactions are declared read-only by appending the keyword READ to the TRANSACTION command.
Read-only transactions lock only those portions of the database actually being read. Fewer locks are required, and they are typically held for less time than are write locks.
To ensure that the software treats implicit transactions that read data (e.g., LIST, REPORT FROM, FIND, COMPUTE, OUTPUT, and so on) as read-only, issue a SET TRANSACTION DEFAULTTYPE READ command.