Hierarchy
SAP_BASIS (Software Component) SAP Basis Component⤷
BC-DB-DB2 (Application Component) DB2 for z/OS⤷
STU2 (Package) CCMS for DB2 for OS/390
Basic Data
| Data Element | DB2GDG_GENERATIONS |
| Short Description | Number of GDG generations |
Data Type
| Category of Dictionary Type | Direct Type Entry | |
| Type of Object Referenced | No Information | |
| Domain / Name of Reference Type | ||
| Data Type | INT4 | 4-byte integer, integer number with sign |
| Length | 10 | |
| Decimal Places | 0 | |
| Output Length | 11 | |
| 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 | 3 | GDG |
| Medium | 15 | GDG generations |
| Long | 25 | Number of GDG generations |
| Heading | 25 | Number of GDG generations |
Documentation
Definition
GDG is the abbrevation for generation data group. This is the administrative unit for a collection of historically related non-VSAM data sets that are arranged in chronological order. GDGs themselves do not contain user data.
Each data set that is part of the GDG is called a generation data set (or short: generation). The generations contain the user data.
A GDG can consist only of a limited number of generations. This number is specified at initial creation of the generation data group base entry, that defines the GDG. Whenever a new generation is created and this number is exceeded, the oldest generation is replaced by the new one. That way, an automatic garbage collection of outdated data sets can be implemented, for instance for backup data sets.
You can configure the number of generations here. Allowed values are 0 to 255. If you specify 0, GDGs are not used by SAP. Any other number will be the number of generations for newly created GDGs in the future. In other words, the "Number of GDG generations" for already existing GDGs will not be changed.
Recommended value
A good number here depends on your environment. Let's assume, that you take up to 3 backups per week (2 incremental and one full backup). If you need to keep the backups of the last 6 months (26 weeks), you should specify 3 * 26 = 78 for "Number of GDG Generations".
History
| Last changed by/on | SAP | 20130604 |
| SAP Release Created in | 700 |
