conventional path/ sql evaluation

[khoshtip_uk]

Hi Guys,

Im having some difficulty undrestanding below note

"Use Direct Path – Direct path exports (DIRECT=Y) allow the export utility to skip the SQL evaluation buffer, whereas the conventional path export executes SQL SELECT statements. With direct path, the data is read from disk into the buffer cache, returning rows directly to the export client. This can offer substantial performance gains, depending on the actual data. When using the direct path, the recordlength parameter should also be used to optimize performance. "

Q: How does Direct path read data from disk into the buffer then ? if its not using select statment ? what is SQL evaluation buffer?

Thanks for your advice

[PAVB]

Why do you think Direct Path option does not uses select statement?

[khoshtip_uk]

I undrestand that its faster because it avoids that part. if its using SQL and the diffrence is in skiping SQL evaluation buffer then what does SQL evaluation buffer involve? is thats about checking SQL syntax?

Thanks

[PAVB]

When using export conventional path you can specify QUERY= parameter to ask export to do something specific like exporting a subset of rows.

The WHERE clause of such sql statement you specify on QUERY= would process on the SQL Evaluation Buffer.