The PER_ROUTINE memory duration

A PER_ROUTINE memory pool is associated with each routine invocation. A routine invocation is one single execution of a UDR within a routine instance.

Tip: The two memory-duration constants PER_ROUTINE and PER_FUNCTION are synonyms for the same memory duration. PER_ROUTINE is the more current name.

When a C UDR allocates PER_ROUTINE memory, this memory is available to code within that single routine invocation of that UDR. The database server reclaims any PER_ROUTINE memory in the memory context when a single invocation of a UDR completes. This memory is actually freed on entry to the next routine invocation. The database server does not reclaim any memory in the memory context with a higher duration than PER_ROUTINE.

In a C UDR, the PER_ROUTINE memory duration is useful for information required for a single UDR invocation. A UDR cannot allocate memory, save a pointer to this memory in static space, and expect the pointer to be valid for the next routine invocation. To save information across invocations, use the user-state pointer of the MI_FPARAM structure. For more information, see Saving a user state.

Several DataBlade API constructor functions allocate their DataBlade API data type structure with a PER_ROUTINE memory duration. The following table shows the DataBlade API data type structures that have a memory duration of PER_ROUTINE.

Table 1. DataBlade API data type structures with a PER_ROUTINE memory duration
DataBlade API data type structure	DataBlade API constructor function	DataBlade API destructor function
UDR arguments that are passed by reference	Routine manager (when it invokes a UDR)	Routine manager (when it exits a UDR)
UDR return value that is passed by value	UDR with its declaration of its return value	Routine manager (when it exits a UDR)
UDR return value that is passed by reference	UDR with call to mi_alloc(), mi_dalloc(), or mi_zalloc()	Routine manager (when it exits a UDR)

The current memory duration is initialized to this default memory duration. The default memory duration is PER_ROUTINE. For more information, see Manage the memory duration.