Oracle教程 2023-02-24

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

本站中文解释

Oracle视图V$eq_message_cache用于管理消息缓存区。此视图中的数据仅可在作业运行时读取，平时是没有任何数据的。

V$eq_message_cache视图可以提供当前系统中消息缓存队列中消息的列表。启动一个应用程序时，队列中可以读取一些消息。如果这些消息中有新的，则V$eq_message_cache视图将被更新，记录这些新消息。

V$eq_message_cache视图可以为应用程序编写者提供有价值的信息，以便在消息处理过程中发现问题和排错。使用V$eq_message_cache视图可以检查消息以及它们在缓冲区中的存储位置，并且可以检查哪一个消息当前已被处理，还有哪一个尚未进行处理。

官方英文解释

V$EQ_MESSAGE_CACHE provides performance statistics of the message cache for Transactional Event Queues (TEQs) at the event stream partition level in the instance.

Column	Datatype	Description
`QUEUE_ID`	`NUMBER`	Queue ID
`EVENT_STREAM_ID`	`NUMBER`	Event stream ID
`PRIORITY`	`NUMBER`	Priority of the event stream partition for dequeue, range `0` – `9`
`EVENT_STREAM_PARTITION_ID`	`NUMBER`	Event stream partition ID
`PARTITION_ID`	`NUMBER`	Queue partition ID
`MAX_MSGS`	`NUMBER`	Maximum number of messages for the event stream partition
`ENQUEUED_MSGS`	`NUMBER`	Number of messages enqueued for the event stream partition
`MSGS_MADE_EXPIRED`	`NUMBER`	Number of messages made expired
`CHUNK_SIZE`	`NUMBER`	The size of the memory chunk for storing messages
`NUM_CHUNKS`	`NUMBER`	Number of chunks for the event stream partition
`NUM_FREE_CHUNKS`	`NUMBER`	Number of free chunks for the event stream partition
`USED_MEMORY_SIZE`	`NUMBER`	Total estimated size of memory in use (in bytes) for the event stream partition
`STATE`	`VARCHAR2(13)`	Event stream partition state. Possible values: `CACHED` (in memory) `UNCACHED` (on disk) `UNCACHED_FREE` `CACHED_FREE` `UNKNOWN`
`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

Note:

This view is available starting with Oracle Database 21c.

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