Conventional Path Export Versus Direct Path Export

Export provides two methods for exporting table data:
■ Conventional path Export
■ Direct path Export
Conventional path Export uses the SQL SELECT statement to extract data from
tables. Data is read from disk into a buffer cache, and rows are transferred to the
evaluatingbuffer.Thedata,afterpassingexpressionevaluation,istransferredtothe
Export client, which then writes the data into the export file.
Direct path Export is much faster than conventional path Export because data is
read from disk into the buffer cache and rows are transferreddirectly to the Export
client. The evaluating buffer is bypassed. The data is already in the format that
Export expects, thus avoiding unnecessary data conversion. The data is transferred
to the Export client, which then writes the data into the export file.

不透過記憶體，直接將資料寫出到磁碟 ,直接匯出資料(透過cached commit scn 載入資料)，資料不需要經過記憶體整合和檢查
這樣減少了sql語句處理的過程.否則exp將使用select來讀取表中的資料，

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