What is Pctused and Pctfree in Oracle?

April 26, 2019 Off By idswater

What is Pctused and Pctfree in Oracle?

PCTFREE is a parameter used to find how much space should be left in a database block for future updates. PCTUSED is a parameter helps Oracle to find when it should consider a database block to be empty enough to be added to the freelist.

What is Pctfree?

The PCTFREE Parameter The PCTFREE parameter sets the minimum percentage of a data block to be reserved as free space for possible updates to rows that already exist in that block.

What is Initrans and Maxtrans?

The INITRANS setting controls Initial Transaction Slots (ITLs). A transaction slot is required for any session that needs to modify a block in an object. The MAXTRANS setting controls the maximum number of ITLs that a block can allocate (usually defaults to 255).

What is Pctfree in SQL?

PCTFREE is a block storage parameter used to specify how much space should be left in a database block for future updates. For example, for PCTFREE=10, Oracle will keep on adding new rows to a block until it is 90% full. This leaves 10% for future updates (row expansion).

What is Pctincrease in Oracle?

The PCTINCREASE parameter in the STORAGE clause determines the degree to which Oracle will automatically increase the size of subsequent extent allocations. This value is expressed as an integer percentage, and is applied to the then-current value of the NEXT parameter.

Where is Data Dictionary kept?

Much of the data dictionary information is kept in the SGA in the dictionary cache, because Oracle constantly accesses the data dictionary during database operation to validate user access and to verify the state of schema objects. All information is stored in memory using the least recently used (LRU) algorithm.

How do you change Initrans?

How to change initrans on table for avoiding enq: TX – allocate…

  1. check if table have child tables with pk-fk relationship, if table have child table(s) then consider to change initrans also for child table(s)
  2. check if Table have indexes, then you must rebuild indexes, and also change initrans for indexes.

What is row chaining in Oracle?

Row chaining occurs when a row can’t physically fit into an Oracle block. Another block is required to store the remainder of the row. Migration of an Oracle row occurs when a row is updated in an Oracle block and the amount of free space in the block is not adequate to store all of the row’s data.

What is the alternate name of data dictionary?

In some relational DBMS products this description is also called the catalog, while in others it is called the directory.