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The MAXIMUM ACTIVE GENERATIONS parameter can be changed at any time on the Database Variable Definition screen. It can also be changed by the CTBDBVCG utility. For more information about the CTBDBVCG utility, see the INCONTROL for z/OS Utilities Guide.
The current (latest) generation of a variable is always generation 0. The previous historical occurrence (value) of a variable is generation –1, and so on.
Therefore, if 50 generations of a variable have been stored, the earliest generation is generation –49. Because the maximum number of generations that Control-M/Analyzer can track is 1000, the largest generation number possible
is –999.
MAXIMUM ACTIVE GENERATIONS is used by Control-M/Analyzer to determine when to delete earlier variable generations to make room for newer ones.
For example, assume that the MAXIMUM ACTIVE GENERATIONS parameter is set to 10 and there are currently 10 active generations (designated 0 through –9). If a rule adds a new value to the variable, the oldest generation, –9, is deleted. The new value becomes generation 0, the previous current value becomes generation –1, and so on.
However, if the MAXIMUM ACTIVE GENERATIONS parameter is set to 10 and there are currently 5 active generations (designated 0 through –4), no values are deleted if a rule adds a new value to the variable. When a new value becomes generation 0, the previous current value becomes generation –1, and so on, resulting in 6 active generations (designated 0 through –5).
Deleted Database variables are assigned a generation value of ***.
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