SSM supervises system resources, such as running tasks and peripheral devices. The SSM engine always tries to keep a resource in its desired state. When the current state differs from the desired state, SSM dispatches an action (as specified in the action text) to restore the resource to its proper state.
The terms desired state and current state refer to the contents of the DESIRED_STATE and CURRENT_STATE columns respectively for a selected resource. You can set these columns to any value that is convenient for your automation needs. For example, you set the current state to INIT, STARTING, STOPPING, ACTIVE, and so on. The current state is the actual state of the resource as it appears on the system. The desired state is the ideal state for a resource. For example, if you want a subsystem to be up (desired state is UP) but the subsystem is down (current state is DOWN), the action text could be a command to start or restart the subsystem.
SSM defines three abstract states, named UP, DOWN, and UNKNOWN. The state names that represent these states for tables are known as the table-relative UP, DOWN, and UNKNOWN states. Each resource table can have its own name for these three states. However, you can define new names to the table-relative UP and DOWN states only when adding a resource table to the SSM directory table.
For example, one table of resources can have ACTIVE defined as its table-relative UP state and INACTIVE defined as its table-relative DOWN state. Another resource table can have ONLINE and OFFLINE defined as its table-relative UP and DOWN states respectively. SSM recognizes the table-relative value by comparing the CURRENT_STATE and DESIRED_STATE columns with the UP_STATE, DOWN_STATE, and UNKNOWN_STATE columns in the directory table.
The CURRENT_STATE and DESIRED_STATE columns are set to the table-relative ACTIVE, INACTIVE, ONLINE, and OFFLINE states. References to the UP state refer to the table-relative state that is designated as UP. For each resource table, the value of the UP and DOWN states is defined in the directory table. The table-relative UP, DOWN, and UNKNOWN states can be referred to symbolically in action text with the corresponding column names of the SSM directory table, such as &UP_STATE, &DOWN_STATE, and &UNKNOWN_STATE.
Note: SSM records all actions that are taken in response to resource state changes in OPSLOG.
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