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Often related to sorting operations, check to see if occurring primarily in temp tablespaces. Solutions 1) Reading from temp tablespaces If the database parameter workarea_size_policy = AUTO: Increase...

Sometimes related to sorting operations, check to see if occurring primarily in temp tablespaces. During Direct Path operations the data is asynchronously read from the database files. At some point t...

Waits on 'db file sequential read' normally occur during index lookups when the block is not in memory and must be read from disk. They are generally considered a 'good' read unless the index being us...

Oracle中db file scattered read等待事件发生在当一个会话在等待一个多数据块的IO请求完成。其典型的发生在当有全表扫描和索引快速扫描INDEX FAST FULL SCAN时。Oracle一次性读取DB_FILE_MULTIBLOCK_READ_COUNT对应的连续数据块，并将它们分散到buffer cache中的buffer中。 换句话说从IO读取上和物理存储的顺序上这些...

This event occurs in the DBWR. It indicates that the DBWR is performing a parallel write to files and blocks. When the last I/O has gone to disk, the wait ends. This wait only occurs in the DBWR proce...

The process has issued multiple I/O requests in parallel to read blocks from data files into memory and is waiting for all requests to complete. This occurs during regular activity when a session batc...

‘cursor: pin * events’等待事件 该类等待事件一般是为了pin相关的子游标 ‘cursor: pin X’ 当一个进程需要以EXCL X mode获得mutex时， 这类需要EXCL X 模式的串行操作包括: 构建一个子游标 某个进程已经以X mode持有该Mutex 一个或多个进程正在reference 该Mutex (shared mutex pin) &nb...

‘cursor: pin * events’等待事件 该类等待事件一般是为了pin相关的子游标 ‘Cursor: pin S on X’ 最常见的等待事件， 进程为了共享操作例如执行pin游标而以SHRD S mode申请mutex， 但是未立即获得。原因是该游标被其他进程以EXCL X mode 持有了。 实际该 cursor: pin S wait on X等待事件往往是由于其他因素诱发的。M...

‘cursor: pin * events’等待事件 该类等待事件一般是为了pin相关的子游标 cursor: pin S 当一个进程以共享pin模式申请一个Mutex，而不能立即获得时，进入cursor: Pin S等待事件。 Mutex Pin是以共享类型的操作，例如执行一个游标。 当一个进程等在cursor: pin S上，说明该进程在对一个共享的mutex pin 参考或取消参考时，有其他...

cursor: mutex * events等待事件用于Cursor Parent 和 Cursor stats类型的操作： ‘cursor: mutex X’ ， 某个进程申请以EXCL mode持有mutex时进入该等待， 该Mutex要么正被其他进程以SHRD模式参考，这导致X mode的申请必须要等待直到Ref count=0， 或者该mutex正被另一个进程以X mode持有。 相关操作...