Home » Oracle » 1z0-117 » What are the two possible causes?
One of your databases supports a mixed workload.
When monitoring SQL performance, you detect many direct paths reads full table scans.
What are the two possible causes?
A. Histograms statistics not available
B. Highly selective filter on indexed columns
C. Too many sort operations performed by queries
D. Indexes not built on filter columns
E. Too many similar type of queries getting executed with cursor sharing disabled
Correct Answer: BD
Explanation/Reference:
Note:
*The direct path read Oracle metric occurs during Direct Path operations when the data is asynchronously read from the database files into the PGA instead of into the SGA data buffer. Direct reads occur under these conditions:
- When reading from the TEMP tablespace (a sort operation)
- When reading a parallel full-table scan (parallel query factotum (slave) processes)
- Reading a LOB segment
*The optimizer uses a full table scan in any of the following cases:
- Lack of Index
- Large Amount of Data
- Small Table
- High Degree of Parallelism
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