Oracle 视图 V$INSTANCE_CACHE_TRANSFER 官方解释，作用，如何使用详细说明
本站中文解释
Oracle视图V$INSTANCE_CACHE_TRANSFER被用来显示实例对模块缓存的加载和卸载的情况。用户可以使用这个视图来查询当前实例中被缓存的模块名称，模块在内存中加载时间，以及模块卸载时间。此视图有一些有用的列，如：
• INSTANCE_NUMBER：指定模块缓存所属的实例编号。
• MODULE：指定模块缓存的名称。
• LOADTIME：模块被加载到内存中的时间。
• UNLOADTIME：模块从内存中卸载的时间。
可以使用这个视图查询指定的模块所需的加载/卸载的时间，进而可以诊断出有问题的模块和优化模块的性能。
官方英文解释
V$INSTANCE_CACHE_TRANSFER displays statistics for the cache blocks transferred among instances.
Oracle keeps multiple versions of data buffered in the buffer cache. The current buffer (or block), CURRENT_BLOCK, is the most up-to-date copy, containing all recent modifications. A consistent read buffer (or block), CR_BLOCK, contains the version of the data at a particular time prior to the current buffer. It is read-consistent (that is, all the data shown in that buffer are consistent for the start time of a query).
Therefore, for the same data block there can be multiple copies in the buffer cache: one current copy, and one or more consistent read copies with data consistent as of different snapshot times.
| Column | Datatype | Description |
|---|---|---|
|
|
|
Instance from which the blocks are transferred |
|
|
|
Class of the cache block |
|
|
|
The number of blocks that were sent by a particular instance but that never arrived in this instance |
|
|
|
The time waited for blocks that were sent by a particular instance but that never arrived in this instance |
|
|
|
CR Block transfers not affected by remote processing delays |
|
|
|
Total time waited for CR blocks from a particular instance (includes the other times) |
|
|
|
The count of CR blocks which were received by this instance from a particular instance after a 2-way round-trip |
|
|
|
The time waited for CR blocks which were received by this instance from a particular instance after a 2-way round-trip |
|
|
|
The count of CR blocks which were received by this instance from a particular instance after a 3-way round-trip |
|
|
|
The time waited for CR blocks which were received by this instance from a particular instance after a 3-way round-trip |
|
|
|
The count of CR Blocks which were directly read from a remote instance via RDMA |
|
Foot 1 |
|
Total time waited to directly read CR blocks from a remote instance via RDMA (in centiseconds) |
|
|
|
CR Block transfers affected by remote contention |
|
|
|
The time waited for CR blocks which were received by this instance from a particular instance and which were delayed by a log flushed on the sending instance |
|
|
|
CR Block transfers affected by remote system load |
|
|
|
The time waited for CR blocks which were received by this instance from a particular instance and which were delayed because LMS was busy |
|
|
|
Current block transfers not affected by remote processing delays |
|
|
|
Total time waited for current blocks from a particular instance (includes the other times |
|
|
|
The count of current blocks which were received by this instance from a particular instance after a 2-way round-trip |
|
|
|
The time waited for current blocks which were received by this instance from a particular instance after a 2-way round-trip |
|
|
|
The count of current blocks which were received by this instance from a particular instance after a 3-way round-trip |
|
|
|
The time waited for current blocks which were received by this instance from a particular instance after a 3-way round-trip |
|
|
|
The count of current blocks which were directly read from a remote instance via RDMA |
|
|
|
Total time waited to directly read current blocks from a remote instance via RDMA (in centiseconds) |
|
|
|
Current block transfers affected by remote contention |
|
|
|
The time waited for current blocks which were received by this instance from a particular instance and which were delayed by a log flushed on the sending instance |
|
|
|
Current block transfers affected by remote system load |
|
|
|
The time waited for current blocks which were received by this instance from a particular instance and which were delayed because LMS was busy |
|
|
|
The ID of the container to which the data pertains. Possible values include:
|
Footnote 1 This column is available starting with Oracle Database 21c.
