SAP ABAP Data Element RA_COUNT64 (Sum of read ahead pages)
Hierarchy
☛
SAP_BASIS (Software Component) SAP Basis Component
⤷
BC-DB-INF (Application Component) Informix
⤷
STUI (Package) Informix Database Monitor
SAP_BASIS (Software Component) SAP Basis Component⤷
BC-DB-INF (Application Component) Informix⤷
STUI (Package) Informix Database Monitor
Basic Data
| Data Element | RA_COUNT64 |
| Short Description | Sum of read ahead pages |
Data Type
| Category of Dictionary Type | D | Domain |
| Type of Object Referenced | No Information | |
| Domain / Name of Reference Type | STUI_INT64 | |
| Data Type | DEC | Counter or amount field with comma and sign |
| Length | 18 | |
| Decimal Places | 0 | |
| Output Length | 24 | |
| Value Table |
Further Characteristics
| Search Help: Name | ||
| Search Help: Parameters | ||
| Parameter ID | ||
| Default Component name | ||
| Change document | ||
| No Input History | ||
| Basic direction is set to LTR | ||
| No BIDI Filtering |
Field Label
| Length | Field Label | |
| Short | 10 | RA_COUNT |
| Medium | 16 | Read ahead pages |
| Long | 0 | |
| Heading | 0 |
Documentation
Definition
Read aheads allow the system to perform more efficient I/O when a need arises to scan multiple sequential pages from disk. This capability is highly desired in DSS systems like BW, where large table and index scans are normal and in certain types of OLTP processing. In an ideal situation, ixda-RA + idx-RA + da-RA should equal RA-pgsused.
However, if the values of RA_PAGES and RA_THRESHOLD are too high, the system may end up reading in more pages for a read ahead than it should. This will result in high bufwaits since the pages being read in will force existing buffer pool pages to be overwritten or, in the case of dirty pages, flushed out to disk.
History
| Last changed by/on | SAP | 20041216 |
| SAP Release Created in | 700 |
