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摘要： 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... 阅读全文

摘要： 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... 阅读全文

摘要： Waits on this event indicate the statement is performing a full table scan or an index range scan. This is often reduced by adding an index or making the index more efficient.SolutionsTune the SQL sta... 阅读全文

摘要： 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... 阅读全文

摘要： 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... 阅读全文

摘要： Often related to sorting operations, check to see if occurring primarily in temp tablespaces.Solutions1) Reading from temp tablespacesIf the database parameter workarea_size_policy = AUTO:Increase the... 阅读全文

摘要： Direct path writes allow a session to queue an I/O write request and continue processing while the OS handles the I/O. If the session needs to know if an outstanding write is complete then it waits on... 阅读全文

摘要： During Direct Path operations, the data is asynchronously written to the database files. At some stage the session needs to make sure that all outstanding asynchronous I/O have been completed to disk.... 阅读全文

摘要： Waits on High Water enqueue occur when allocating space beyond the high water mark of a segment during insert operations. Also, this wait occurs when reclaiming free space in lob segments after delete... 阅读全文

摘要： Sessions waiting on this event are waiting on locks held during materialized view operations (such as refresh, alter) to prevent concurrent operations on the same materialized view.SolutionsA material... 阅读全文