Oracle 视图 V$EQ_MESSAGE_CACHE_ADVICE 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_ADVICE提供了对Event Message Cache的详细情况分析，例如最大的CACHE_HITS，优先期最长的HIT_CNT，缓存命中率CACHE_HIT_RATE等。该视图也可以显示当前时刻系统保持的活动消息和查询的消息。

使用方法：

1、查询Event Message Cache的分析监控信息：

SELECT message_type, sum(hits) cache_hits, max(hit_cnt) longest_hit_cnt, round(cpu_hits/hits,2) async_cpu_ratio, round((hits-cpu_hits)/hits*100,2) cache_hit_rate FROM v$eq_message_cache_advice GROUP BY message_type;

2、查询当前正在进行的消息:

SELECT message_type, message_text, holder_name, object_name, object_type, decode(status,’EXECUTING’,’USER_ACTIVE’,’QUEUED’) status FROM v$eq_message_cache_advice WHERE status IN (‘EXECUTING’,’QUEUED’);

官方英文解释

V$EQ_MESSAGE_CACHE_ADVICE shows simulated metrics for a range of potential message cache sizes for Transactional Event Queues (TEQs). This view assists in cache sizing by providing information in the form of metrics as described below.

Column	Datatype	Description
`SIZE_FOR_ESTIMATE`	`NUMBER`	Cache size for simulation (in megabytes)
`SIZE_FACTOR`	`NUMBER`	Size factor with respect to the current cache size
`ESTD_SIZE_TYPE`	`VARCHAR2(9)`	Possible values: `MINIMUM`: This cache size is required to have all dequeues in-memory (no uncached). `CURRENT`: This is the current size of the message cache. `MAXIMUM`: This cache size is required to have zero evictions. `NULL`: This is the value in all other cases.
`ESTD_CACHED_PARTITIONS`	`NUMBER`	Estimated number of cached event stream partitions for this size
`ESTD_UNCACHED_PARTITIONS`	`NUMBER`	Estimated number of uncached event stream partitions for this size
`ESTD_EVICTIONS`	`NUMBER`	Estimated number of event stream partitions evicted for this size
`ESTD_EVICTION_RATE`	`NUMBER`	Estimated number of event stream partitions getting evicted per minute
`ESTD_FG_UNEVICTIONS`	`NUMBER`	Estimated number of event stream partitions unevicted by foreground processes
`ESTD_FG_UNEVICTION_RATE`	`NUMBER`	Estimated number of event stream partitions getting unevicted by foreground processes
`ESTD_BG_UNEVICTIONS`	`NUMBER`	Estimated number of event stream partitions unevicted by background processes
`ESTD_BG_UNEVICTION_RATE`	`NUMBER`	Estimated number of event stream partitions getting unevicted by background processes
`ESTD_BG_PROCESSES`	`NUMBER`	Estimated number of background processes required for this size
`TOTAL_ENQUEUE_RATE`	`NUMBER`	Simulated number of messages being enqueued per second
`TOTAL_DEQUEUE_RATE`	`NUMBER`	Simulated number of messages being dequeued per second
`AVG_PARTITION_SIZE`	`NUMBER`	Simulated average number of messages per cached event stream partitions
`AVG_PARTITION_MEMORY`	`NUMBER`	Simulated average memory per cached event stream partition (in megabytes)
`AVG_EVICTION_TIME`	`NUMBER`	Simulated average time to evict a cached event stream partition (in milliseconds)
`AVG_UNEVICTION_TIME`	`NUMBER`	Simulated average time to unevict a cached event stream partition (in milliseconds)
`FLAGS`	`NUMBER`	Reserved for internal use
`SIMULATION_TIME`	`NUMBER`	Amount of time that was simulated for (in minutes)
`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.