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1Z0-062 · Question #364

DAILY_ORDS_LST is created in locally managed tablespace ORDERS_TBS which uses automatic segment space management. Which two are true? (Choose two.)

The correct answer is B. 20% of each data block in the table is reserved for row updates D. PCTFREE can help reduce row migration during updates. PCTFREE reserves a percentage of space in data blocks for future row updates, which helps prevent row migration. While automatic segment space management (ASSM) handles free space, PCTFREE's role in reserving space for updates remains relevant.

Managing Database Storage Structures

Question

DAILY_ORDS_LST is created in locally managed tablespace ORDERS_TBS which uses automatic segment space management. Which two are true? (Choose two.)

Options

  • A80% of every data block in daily_ords_list is reserved for row inserts
  • B20% of each data block in the table is reserved for row updates
  • CPCTFREE can help to minimize row chaining during inserts
  • DPCTFREE can help reduce row migration during updates
  • EPCTFREE eliminates row chaining during inserts

How the community answered

(33 responses)
  • A
    3% (1)
  • B
    82% (27)
  • C
    12% (4)
  • E
    3% (1)

Why each option

PCTFREE reserves a percentage of space in data blocks for future row updates, which helps prevent row migration. While automatic segment space management (ASSM) handles free space, PCTFREE's role in reserving space for updates remains relevant.

A80% of every data block in daily_ords_list is reserved for row inserts

PCTFREE reserves space for updates, not inserts, and 80% is not a default or typical reservation for inserts; PCTUSED (not applicable with ASSM) relates to space usable for new rows before freeing.

B20% of each data block in the table is reserved for row updatesCorrect

PCTFREE reserves a specified percentage of free space within each data block to accommodate future updates to existing rows. If PCTFREE is set to 20, then 20% of each data block in the table is reserved for these row updates.

CPCTFREE can help to minimize row chaining during inserts

PCTFREE primarily minimizes row migration for updates; row chaining during inserts typically occurs when a row's initial size exceeds the block size, which PCTFREE does not address.

DPCTFREE can help reduce row migration during updatesCorrect

PCTFREE helps reduce row migration by ensuring that sufficient free space is available in a data block for existing rows to grow when they are updated, thus preventing the row from having to move to a different block.

EPCTFREE eliminates row chaining during inserts

PCTFREE cannot eliminate row chaining during inserts, as chaining for inserts happens when a row's initial size is too large for a single block, irrespective of reserved space for updates.

Concept tested: PCTFREE and row management

Source: https://docs.oracle.com/en/database/oracle/oracle-database/19/sqlrf/CREATE-TABLE.html#GUID-F9CE0CCF-1300-4593-B285-1A90F562468B__BABECJIA

Topics

#PCTFREE#row chaining#row migration#segment space management

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