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mysqlnd_ms_xa_gc(3) [php man page]

MYSQLND_MS_XA_GC(3)							 1						       MYSQLND_MS_XA_GC(3)

mysqlnd_ms_xa_gc - Garbage collects unfinished XA transactions after severe errors

SYNOPSIS

       int mysqlnd_ms_xa_gc (mixed  $connection, [string  $gtrid], [boolean  $ignore_max_retries])

DESCRIPTION

	Garbage collects unfinished XA transactions.

	The XA protocol is a blocking protocol. There exist cases when servers participating in a global transaction cannot make progress when the
       transaction coordinator crashes or disconnects. In such a case, the MySQL servers keep waiting for instructions to finish the  XA  transac-
       tion in question. Because transactions occupy resources, transactions should always be terminated properly.

	Garbage  collection requires configuring a state store to track global transactions. Should a PHP client crash in the middle of a transac-
       tion and a new PHP client be started, then the built-in garbage collection can learn about the aborted global transaction and terminate it.
       If you do not configure a state store, the garbage collection cannot perform any cleanup tasks.

	The  state  store  should  be  crash-safe  and be highly available to survive its own crash. Currently, only MySQL is supported as a state
       store.

	Garbage collection can also be performed automatically in the background. See the plugin configuration	directive  garbage_collection  for
       details.

       Note

	      Experimental

	       The feature is currently under development. There may be issues and/or feature limitations. Do not use in production environments.

PARAMETERS

	      o $connection
		- A MySQL connection handle obtained from any of the connect functions of the mysqli, mysql or PDO_MYSQL extensions.

	      o $gtrid
		-  Global  transaction	identifier  (gtrid). If given, the garbage collection considers the transaction only. Otherwise, the state
		store is scanned for any unfinished transaction.

	      o $ignore_max_retries
		- Whether to ignore the plugin configuration max_retries setting. If garbage collection continuously  fails  and  the  max_retries
		limit  is  reached prior to finishing the failed global transaction, you can attempt further runs prior to investigating the cause
		and solving the issue manually by issuing appropriate SQL statements on the participants.  Setting  the  parameter  has  the  same
		effect as temporarily setting max_retries = 0.

RETURN VALUES

	Returns TRUE if garbage collection was successful. Otherwise, returns FALSE

SEE ALSO

       Quickstart XA/Distributed transactions, Runtime configuration, State store configuration, mysqlnd_ms_get_stats(3).

PHP Documentation Group 												       MYSQLND_MS_XA_GC(3)

Check Out this Related Man Page

SET 
TRANSACTION(7)						   SQL Commands 						SET TRANSACTION(7)

NAME

       SET TRANSACTION - set the characteristics of the current transaction

SYNOPSIS

       SET TRANSACTION ISOLATION LEVEL { READ COMMITTED | SERIALIZABLE }
       SET SESSION CHARACTERISTICS AS TRANSACTION ISOLATION LEVEL
	   { READ COMMITTED | SERIALIZABLE }

DESCRIPTION

       This command sets the transaction isolation level. The SET TRANSACTION command sets the characteristics for the current SQL-transaction. It
       has no effect on any subsequent transactions. This command cannot be used after the first query	or  data-modification  statement  (SELECT,
       INSERT, DELETE, UPDATE, FETCH, COPY) of a transaction has been executed. SET SESSION CHARACTERISTICS sets the default transaction isolation
       level for each transaction for a session. SET TRANSACTION can override it for an individual transaction.

       The isolation level of a transaction determines what data the transaction can see when other transactions are running concurrently.

       READ COMMITTED
	      A statement can only see rows committed before it began. This is the default.

       SERIALIZABLE
	      The current transaction can only see rows committed before first query or data-modification statement was executed in this  transac-
	      tion.

	      Tip:  Intuitively,  serializable	means that two concurrent transactions will leave the database in the same state as if the two has
	      been executed strictly after one another in either order.

NOTES

       The session default transaction isolation level can also be set with the command

       SET default_transaction_isolation = 'value'

       and in the configuration file. Consult the Administrator's Guide for more information.

COMPATIBILITY

   SQL92, SQL99
       SERIALIZABLE is the default level in SQL. PostgreSQL does not provide the isolation levels READ UNCOMMITTED and REPEATABLE READ. Because of
       multiversion concurrency control, the SERIALIZABLE level is not truly serializable. See the User's Guide for details.

       In  SQL	there  are two other transaction characteristics that can be set with these commands: whether the transaction is read-only and the
       size of the diagnostics area.  Neither of these concepts are supported in PostgreSQL.

SQL - Language Statements					    2000-11-24							SET TRANSACTION(7)
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