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Celonis Product Documentation

Action Flow execution, cycles, and phases

Celonis platform is a transactional system, similar to relational databases. Each Action Flow execution starts with the initialization phase, continues with at least one cycle composed of the operation and commit/rollback phases, and ends with the finalization phase:

  1. initialization

  2. cycle #1

    1. operation (reading or writing)

    2. commit or rollback

  3. cycle #2

    1. operation (reading or writing)

    2. commit or rollback

  4. ---

  5. cycle #N

    1. operation (reading or writing)

    2. commit or rollback

  6. finalization

Initialization

During the initialization phase, all necessary connections (connection to a database, email service, etc.) are created. They are also checked if each module is capable of performing their intended operation(s).

Cycles

Each cycle represents an undividable unit of work composed of a series of operations. It is possible to set the maximum number of cycles in the Action Flow settings. The default number is 1.

Operation

During the operation phase reading and/or writing operation is performed:

  • The reading operation consists of obtaining data from a service that will then be processed by other modules according to a predefined Action Flow. E.g. the Dropbox > Watch files module returns new bundles (files) created since the last Action Flow execution.

  • The writing operation consists of sending data to a given service for further processing. E.g. the Dropbox > Upload a file module uploads a file to a Dropbox folder.

Commit

If the operation phase is successful for all modules, the commit phase begins during which all operations performed by the modules are committed. This means that Celonis platform sends information to all the services involved in the operation phase about its success.

Rollback

If an error occurs during the operation or commit phase on any module, the phase is aborted and the rollback phase is started, making all operations during the given cycle void. Some modules do not support rollback and operations performed by these modules cannot be taken back. For more information see the ACID modules section.

Finalization

During the finalization phase, open connections (e.g. FTP connections, database connections, etc.) are closed and the Action Flow is completed.

ACID modules

The modules that support rollback (transactional modules) are tagged with the ACID tag:

Scenario_execution_cycles_phases_1.png

The modules not tagged with this tag do not support rollback and cannot be reverted back to their initial state in case of an error in other modules.

A typical example is the Email Send an email module. Once the module sends an email during its operation phase, the sending cannot be undone.

Examples

Transfer of bundles between databases

The following example shows how to connect three ACID modules. The aim of the below Action Flow is to get new rows from a MySQL database, insert (transfer) them into a MSSQL database and then insert the IDs of the rows from the MSSQL database into a PostgreSQL database.

Scenario_execution_cycles_phases_2.jpeg

When the Action Flow starts, the initialization phase is performed first. Celonis platform verifies connections to the MySQL, MSSQL and PostgreSQL databases one at a time. If everything goes well and the connections are successful, Celonis platform moves on to the operation phase. If an error occurs, the finalization phase starts instead of the operation phase and the Action Flow is terminated.

Next comes the operation phase. A preset procedure selects (reads) the table rows (bundles) from MySQL. Those rows are then passed to the next module that writes them to a selected table in the MSSQL database. If everything is in order, the last PostgresSQL procedure is called to insert the row IDs returned by the preceding module into the table.

If the operation phase is completed successfully, the commit phase begins. Celonis platform calls the SQL COMMIT command for each database and the write operations will be committed.

However, if the operation or commit phase fails due to an error, (e.g. connection failure), Celonis platform calls rollback. During the rollback phase, Celonis platform goes through all modules one after another and executes the SQL ROLLBACK command for each module to revert each database back to its initial state.

Finally, during the finalization phase, each module will close its connection to the database.