Oracle教程 2023-02-24

Oracle 视图 V$FLASHBACK_TXN_GRAPH 官方解释，作用，如何使用详细说明

本站中文解释

Oracle视图V$FLASHBACK_TXN_GRAPH用于显示当前Oracle实例中全局事务图表，它以有向图显示事务图，该图可以用来查看全局事务中父子事务之间的关系。

用途：

1.通过V$FLASHBACK_TXN_GRAPH视图可以帮助查找事务依赖项，在做恢复时，可以依据该视图数据正确的恢复全局事务。

2.当事务出现死锁时，可以使用该视图V$FLASHBACK_TXN_GRAPH找出死锁的原因，当发现死锁之后，可以采取对应的方式来解决死锁的问题。

3.使用该视图V$FLASHBACK_TXN_GRAPH可以帮助查找和符合特定条件的事务，可以为任务定位和调整性能提供帮助。

使用方式：

可以使用SQL查询来查看Oracle实例中全局事务之间的图表，具体查询语句如下：

SELECT * FROM V$FLASHBACK_TXN_GRAPH;

官方英文解释

V$FLASHBACK_TXN_GRAPH displays a tabular representation of the transaction dependency graph. For each dependency edge, there could be multiple rows, one for each conflicting operation.

This view is relevant AFTER a compensating transaction has been started through the DBMS_FLASHBACK.TRANSACTION_BACKOUT() set of functions, and is no longer relevant once the compensating transaction is either committed or rolled back. It also provides a tabular representation of the undo SQL that is not available through the CLOB XML construct in the DBA_FLASHBACK_TXN_REPORT view.

Column	Datatype	Description
`COMPENSATING_XID`	`RAW(8)`	Transaction ID of the compensating transaction
`COMPENSATING_TXN_NAME`	`VARCHAR2(255)`	Name of the compensating transaction
`XID`	`RAW(8)`	Transaction ID of a relevant transaction found in memory
`TXN_NAME`	`VARCHAR2(255)`	Name of the transaction with `XID` as the transaction ID; NULL if none
`PARENT_XID`	`RAW(8)`	Parent transaction ID (for a PDML transaction)
`INTERESTING`	`NUMBER`	If the transaction is in the transaction dependency graph
`ORIGINAL`	`NUMBER`	If the transaction is part of the input set provided
`BACKOUT_SEQ`	`NUMBER`	Order in which the transaction has been backed out
`NUM_PREDS`	`NUMBER`	Number of predecessors of the transaction specified by `XID` in the transaction graph
`NUM_SUCCS`	`NUMBER`	Number of successors of the transaction specified by `XID` in the transaction graph
`DEP_XID`	`RAW(8)`	One dependent transaction ID of the transaction specified by `XID`. This is a particular child of `XID`.
`DEP_TXN_NAME`	`VARCHAR2(255)`	Transaction name, if any, for the transaction specified by `DEP_XID`
`TXN_CONF_SQL_ID`	`NUMBER`	SQL ID of undo SQL executed in the context of `XID` which conflicts with the dependent transaction
`DEP_TXN_CONF_SQL_ID`	`NUMBER`	SQL ID of undo SQL executed in the context of `DEP_XID` which conflicts with `XID`
`CONFLICT_TYPE`	`VARCHAR2(32)`	The type of conflict that the conflict resolution method is used to resolve: delete, uniqueness, or update
`CON_ID`	`NUMBER`	The ID of the container to which the data pertains. Possible values include: `0`: This value is used for rows containing data that pertain to the entire CDB. This value is also used for rows in non-CDBs. `1`: This value is used for rows containing data that pertain to only the root n: Where n is the applicable container ID for the rows containing data

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