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At runtime, characteristics at the global, session, and next-transaction scope levels can be set indirectly using the SET TRANSACTION  statement, as described previously. They can also be set directly using the SET  statement to assign values to the transaction_isolation  and transaction_read_only system variables: 

• SET TRANSACTION  permits optional GLOBAL  and SESSION  keywords for setting transaction characteristics at different scope levels. 

•The SET  statement for assigning values to the transaction_isolation  and transaction_read_only  system variables has syntaxes for setting these variables at different scope levels. 

The following tables show the characteristic scope level set by each SET TRANSACTION  and variable- assignment syntax. 

<img src='content_image/734515.jpg'>

<img src='content_image/734516.jpg'>

It is possible to check the global and session values of transaction characteristics at runtime: 

## 13.3.8 XA Transactions 

SELECT @@GLOBAL.transaction_isolation, @@GLOBAL.transaction_read_only; SELECT @@SESSION.transaction_isolation, @@SESSION.transaction_read_only; 

Support for XA transactions is available for the InnoDB  storage engine. The MySQL XA implementation is based on the X/Open CAE document Distributed Transaction Processing: The XA Specification . This document is published by The Open Group and available at http://www.opengroup.org/public/pubs/catalog/ 

