RPG opcodes & indicators

SETLL positions at the first key greater than or equal to the search argument. SETGT positions beyond equal keys. Subsequent reads determine the actual record transfer. Both are positioning operations.

Use SETGT when the boundary is exclusive, such as moving beyond a completed key group. Consider key order and partial-key behavior. Test exact match, absent key, before-first, and after-last cases to explain the difference convincingly.

READP retrieves the previous record in the access-path sequence. READPE retrieves a previous record while restricting processing to the equal-key group. Correct positioning before backward traversal is essential.

For reverse processing of a key group, position after the group and then read backward using the matching key. Check the appropriate status after every read. Do not describe previous as necessarily a smaller business value when the access path includes descending key fields.

For operations that support it, the E extender routes operation errors to status handling that the program can inspect, such as %ERROR and %STATUS. MONITOR/ON-ERROR establishes a structured exception-handling region for eligible exceptions.

Choose a consistent local handling strategy, and remember that already-handled errors do not automatically follow the same path as unhandled exceptions. Embedded SQL reports its own SQL status; it must be checked explicitly rather than assumed to enter RPG ON-ERROR.

EXFMT writes a display record format and then reads the response. READC retrieves changed subfile records, allowing an application to process the user’s selected or edited rows. Their roles are different from ordinary disk-file scanning.

Validate function keys and user options before updates. Subfile changed-state behavior, including indicators that mark records for reprocessing, affects what READC returns. Keep screen interaction outside long database transactions where practical.

CLEAR sets an item to its type-appropriate default clearing value. RESET restores the saved initialization/reset value according to the item’s definition and runtime rules. INZ defines initialization at the relevant storage lifetime.

Use these deliberately for request state. A business default of status NEW is not necessarily the same as blanks. Test data structures containing initialized fields, and avoid assuming that each procedure call reconstructs all static storage from its declarations.

EVAL-CORR assigns corresponding compatible subfields by name according to RPG’s rules. A whole-structure assignment has its own type and layout requirements. Neither should be used without understanding which fields are actually copied.

For request mapping, verify renamed, absent, incompatible, and nested fields explicitly. Initialize the target deliberately so fields not assigned do not retain stale request data. A statement compiling successfully is not a substitute for confirming the intended mapping.

A traditional subroutine invoked with EXSR shares the enclosing program’s context and has no independent typed parameter interface like a subprocedure. A subprocedure can define local data, parameters, a return value, and a reusable call contract.

Use procedures to make dependencies and testing clearer, but do not assume merely moving code removes global references. During refactoring, identify every input, output, file side effect, and indicator dependency, then express them through an intentional interface.

Numeric indicators often combine unrelated meanings such as file status, screen options, and business flags. A distant operation can alter a shared indicator, making the control flow difficult to reason about.

Replace business-state uses with named Boolean fields where feasible, and use explicit file status BIFs for I/O. Preserve externally defined display indicators where needed through named mappings. Refactor incrementally because an apparently unused indicator may still control an output specification or DDS condition.