List down various roles played by the transaction coordinator

List down various roles played by the transaction coordinator, What are the roles of a transaction coordinator in distributed database transactions? Roles of transaction coordinator

More than one computers (servers) are connected and the database resources stored in them are used by transactions that are running in those computers. A transaction coordinator is a site (computer) which is part of a distributed database. Whenever an user request for some information, the request is actually reaching to a single site. If the requested information is available with that site, then the transaction manager of that particular site handles the request and answers. If the information is not available (or partly available), then the transaction manager acts as the coordinator for that transaction and forward the request to other sites where the data might be available. Here, the transaction coordinator plays different roles. They are as follows;
 

• Starting the execution of a transaction initiated at that site.

• Breaking the transaction into a set of sub-transactions if needed.

• Distributing the sub-transactions to different sites.

• Coordinating the completion of the transaction.

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