| Key | Description | Value |
| user_time | user CPU time | [SinceStart, SinceLast] |
| system_time | system CPU time | [SinceStart, SinceLast] |
| cpu_time | total CPU time (user + system) | [SinceStart, SinceLast] |
| real_time | absolute time | [SinceStart, SinceLast] |
| local_stack | local stack sizes (control, environments, choices) | [UsedSize, FreeSize] |
| global_stack | global stack sizes (compound terms) | [UsedSize, FreeSize] |
| trail_stack | trail stack sizes (variable bindings to undo) | [UsedSize, FreeSize] |
| cstr_stack | constraint trail sizes (finite domain constraints) | [UsedSize, FreeSize] |
| Key is neither a variable nor a valid key | domain_error(statistics_key, Key) | |
| Value is neither a variable nor a list of two elements | domain_error(statistics_value, Value) | |
| Value is a list of two elements and an element E is neither a variable nor an integer | type_error(integer, E) | |
| Time is neither a variable nor an integer | type_error(integer, Time) | |