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

本站中文解释

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V$LOGMNR_LATCHES是一个视图，它可以帮助DBA来查看Oracle实例中LOGMINER用到的信号量(Latches)，更加方便地了解它们在数据库中是如何被使用的。

LOGMINER（日志分析器）是Oracle数据库提供的一个强大的分析查看器，可帮助DBA查看和分析数据库中保存的更改日志，了解发生了什么样的变化以及它是如何执行的。要使用LOGMINER，必须要先启动它，而V$LOGMNR_LATCHES视图就是用于查看LOGMINER是否启用的 latching 值的。

V$LOGMNR_LATCHES除了可以查看LOGMINER是否启用外，还会报告 LOGMINER 作为活动运行着的其他信息，如：

• 任务计数 – 显示LOGMINER在解析日志的任务的完成情况
• 实例保持计数 – 显示LOGMINER当前与实例的连接数
• 缓存块复制计数 – 显示LOGMINER已经复制多少个缓存块

通过使用 V$LOGMNR_LATCHES 视图，DBA 就可以精确查看 LOGMINER 是否处于活动状态，以及它在此期间从日志中复制了多少个缓存块。总之，这个视图给 DBA 提供了一种方便的方法来了解 Oracle 数据库实例中 LOGMINER 的状态和行为。

官方英文解释

V$LOGMNR_LATCH can be joined with the V$LATCH and the V$LATCH_CHILDREN views to obtain statistics about different latches used by active LogMiner persistent sessions.

A persistent LogMiner session is created either by starting Data Guard SQL Apply on a logical standby database for the first time or by creating a Replication capture.

Column Datatype Description

SESSION_ID

NUMBER

Unique identifier of the LogMiner persistent session

NAME

VARCHAR2(32)

Name of the Latch:

  • LogMiner internal state – Identifies the latch that protects communications between the LogMiner READER, PREPARER, and BUILDER processes

  • LogMiner memory allocation – Identifies the latch that protects all memory allocation and deallocation inside LogMiner

  • LogMiner transaction list – Identifies the latch that protects interaction between the LogMiner layer and its clients during Data Guard SQL Apply on a logical standby database

CHILD_ADDR

RAW(4 | 8)

Address of the child latch object. This column matches the corresponding ADDR column in the V$LATCH_CHLDREN view

STATE

VARCHAR2(6)

State of the Latch:

  • UNINIT – The latch structure is uninitialized; that is, it is not currently assigned to any LogMiner persistent session

  • READY – The latch structure is being used by a persistent LogMiner session

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

See Also:

  • “V$LATCH”

  • “V$LATCH_CHILDREN”


数据运维技术 » Oracle 视图 V$LOGMNR_LATCH 官方解释，作用，如何使用详细说明
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