Note the optimizer is able to adapt plans on the fly

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Note: * The optimizer is able to adapt plans on the fly by predetermining multiple subplans for portions of the plan. * Adaptive plans, introduced in Oracle Database 12c, enable the optimizer to defer the final plan decision for a statement until execution time. The optimizer instruments its chosen plan (the default plan) with statistics collectors so that it can detect at runtime, if its cardinality estimates differ greatly from the actual number of rows seen by the operations in the plan. If there is a significant difference, then the plan or a portion of it will be automatically adapted to avoid suboptimal performance on the first execution of a SQL statement.
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References: QUESTION 61 You create a new pluggable database, HR_PDB, from the seed database. Which three tablespaces are created by default in HR_PDB? (Choose three.) A. SYSTEM B. SYSAUX C. EXAMPLE D. UNDO E. TEMP F. USERS Correct Answer: ABE Section: (none) Explanation Explanation/Reference: Explanation: * A PDB would have its SYSTEM, SYSAUX, TEMP tablespaces.It can also contains other user created tablespaces in it. * Oracle Database creates both the SYSTEM and SYSAUX tablespaces as part of every database. * tablespace_datafile_clauses Use these clauses to specify attributes for all data files comprising the SYSTEM and SYSAUX tablespaces in the seed PDB. Incorrect: Not D: a PDB can not have an undo tablespace. Instead, it uses the undo tablespace belonging to the CDB. Note: * Example: CONN [email protected] SELECT tablespace_name FROM dba_tablespaces; TABLESPACE_NAME ------------------------------ SYSTEM SYSAUX TEMP USERS SQL> QUESTION 62 Which two statements are true about variable extent size support for large ASM files? (Choose two.) A. The metadata used to track extents in SGA is reduced. B. Rebalance operations are completed faster than with a fixed extent size C. An ASM Instance automatically allocates an appropriate extent size. D. Resync operations are completed faster when a disk comes online after being taken offline. E. Performance improves in a stretch cluster configuration by reading from a local copy of an extent. Correct Answer: AC Section: (none) Explanation Explanation/Reference:
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Explanation: A: Variable size extents enable support for larger ASM datafiles, reduce SGA memory requirements for very large databases (A), and improve performance for file create and open operations. C: You don't have to worry about the sizes; the ASM instance automatically allocates the appropriate extent size. Note: * The contents of ASM files are stored in a disk group as a set, or collection, of data extents that are stored on individual disks within disk groups. Each extent resides on an individual disk. Extents consist of one or more allocation units (AU). To accommodate increasingly larger files, ASM uses variable size extents.
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  • Fall '19
  • Oracle Database

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