constants group TransactionIsolation in module com::sun::star::sdbc::

(Global Index)

Syntax

constants group TransactionIsolation;

Description

distinguishes different possible transaction isolation levels.

Constants Summary

NONE indicates that transactions are not supported.

READ_UNCOMMITTED Dirty reads, non-repeatable reads and phantom reads can occur. This level allows a row changed by one transaction to be read by another transaction before any changes in that row have been committed (a "dirty read"). If any of the changes are rolled back, the second transaction will have retrieved an invalid row.

READ_COMMITTED Dirty reads are prevented; non-repeatable reads and phantom reads can occur. This level only prohibits a transaction from reading a row with uncommitted changes in it.

REPEATABLE_READ Dirty reads and non-repeatable reads are prevented; phantom reads can occur. This level prohibits a transaction from reading a row with uncommitted changes in it, and it also prohibits the situation where one transaction reads a row, a second transaction alters the row, and the first transaction rereads the row, getting different values the second time (a "non-repeatable read").

SERIALIZABLE Dirty reads, non-repeatable reads and phantom reads are prevented. This level includes the prohibitions in REPEATABLE_READ and further prohibits the situation where one transaction reads all rows that satisfy a WHERE condition, a second transaction inserts a row that satisfies that WHERE condition, and the first transaction rereads for the same condition, retrieving the additional "phantom" row in the second read.

Field Details



NONE

Syntax

const long  NONE =  0;

Description

indicates that transactions are not supported.


READ_UNCOMMITTED

Syntax

const long  READ_UNCOMMITTED =  1;

Description

Dirty reads, non-repeatable reads and phantom reads can occur. This level allows a row changed by one transaction to be read by another transaction before any changes in that row have been committed (a "dirty read"). If any of the changes are rolled back, the second transaction will have retrieved an invalid row.


READ_COMMITTED

Syntax

const long  READ_COMMITTED =  2;

Description

Dirty reads are prevented; non-repeatable reads and phantom reads can occur. This level only prohibits a transaction from reading a row with uncommitted changes in it.


REPEATABLE_READ

Syntax

const long  REPEATABLE_READ =  4;

Description

Dirty reads and non-repeatable reads are prevented; phantom reads can occur. This level prohibits a transaction from reading a row with uncommitted changes in it, and it also prohibits the situation where one transaction reads a row, a second transaction alters the row, and the first transaction rereads the row, getting different values the second time (a "non-repeatable read").


SERIALIZABLE

Syntax

const long  SERIALIZABLE =  8;

Description

Dirty reads, non-repeatable reads and phantom reads are prevented. This level includes the prohibitions in REPEATABLE_READ and further prohibits the situation where one transaction reads all rows that satisfy a WHERE condition, a second transaction inserts a row that satisfies that WHERE condition, and the first transaction rereads for the same condition, retrieving the additional "phantom" row in the second read.

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