All IBM Application Gateway (IAG) YAML configuration files must contain a 'version' indicator.
version: 19.12 ...
This version number specifies the version of the IAG container that the configuration was first authored for. The IAG container uses this version number to determine how it should interpret the configuration data.
The version number is specified in the format YY.MM, where 19.12 corresponds to the December 2019 release of IAG.
When the IAG configuration provided spans multiple YAML files, each YAML file must be authored for the same IAG version and contain the same 'version' string. The IAG container will not start if configuration data containing more than one version is found.
For further information about specifying the configuration data in multiple documents, see Configuration.
When replacing an IAG container with a newer version, existing configuration files can be used as-is without modifying the 'version' indicator. All versions of IAG are able to interpret configuration YAML from any previous version without modification.
To make use of capabilities in a newer version of IAG, the configuration data must be updated to the minimum version indicated by the 'since' field in the YAML Reference.
Note that additional changes to the YAML configuration data may be required when moving to a newer version. Refer to What's New for information about changes between versions and the YAML Reference pages for information about configuration YAML schema.