What's the operation phase?

After the completion of the project life cycle, the operation phase starts.  It means the beginning of the purpose for which the project was undertaken.  Suppose the project is for the purpose of setting up of a manufacturing unit for the production of textile: the operation phase is from the "Trial run" first and commencement of the  commercial production onwards....

The operation phase is not a phase in the project life cycle, because it starts after the project is completed. The operation phase is the phase when the product/service (resulting from the project) starts to be used (in other words, in operation mode).The operation phase is also referred to as the maintenance phase.

For example, let's assume that your project was about creating an accounting software. Once the project is done, and the accounting software starts being used by the intended users (the accountants), then you are in the operation phase.

I found a lot of descriptions about IT systems so I will put it in my own words. In the operations and maintenance) phase the complete Project is in use , all the mechanical features are tested, adjusted, gas , water , electrical equipment's and infrastructure is tested. airco (or heating) is fully tested and adjusted and the maintenance procedures are tested as well. But also simple things as locks are all tested. Everything needs to be according to the specs.

The operation phase is not a phase in the project life cycle, because it starts after the project is completed.

The operation phase is also referred to as the maintenance phase.

Endorse Mr. Krishna answer

It's Maintenance phase which begins after the project hand over directly 

In Iraqi's specifications It's one year after hand over 

The operation phase is not a phase in the project life cycle, because it starts after the project is completed. The operation phase is the phase when the product/service (resulting from the project) starts to be used (in other words, in operation mode).

operations is the stage where the product / service output has begun successfully after thoroughly testing, commissioning and closing the defects after handing over a project.

That is the phase that starts after the completion of the project. For example, the project is to build a commercial building. The operations phase would be when we start using the building after the end of the project.

Operation phase means when the installation of any Plant or Equipment is complete, the next step will be operation phase. In operation phase, the plant or equipment give the output as expected

In case of civil engineering project, when the a building or a bridge or a road is handed over to the sponsoring authority, the next step is the operation phase i.e. use of the building, or bride or road then starts