Heuristic (Tyrex API JavaDoc)

Overview

Package

Class

Tree

Deprecated

Help

PREV CLASS NEXT CLASS

FRAMES NO FRAMES

SUMMARY: NESTED | FIELD | CONSTR | METHOD

DETAIL: FIELD | CONSTR | METHOD

tyrex.tm
Interface Heuristic

public interface Heuristic

Defines values for different heuristic decisions. During prepare, commit and rollback the transaction manager will reach certain heuristic decisions regarding the transaction and its resources.

If the transaction involves no resources, the heuristic decision will be that the transaction is read-only and does not need commit or rollback. If the transaction has been marked for roll back, the heuristic decision will be to roll back the transaction. Otherwise, if the transaction is being commited the heuristic decision is to commit the transaction.

During prepare/commit/rollback, certain resources may not respond properly and the heuristic decision about the transaction might change. For example, attempting to commit a transaction that has one resource that fails to prepare will change it's heuristic decision to rollback.

In the event that two resources made conflicting decisions, the heuristic decision will be mixed. This will cause the transaction to attempt and roll back as many remaining resources as possible.

The heuristic outcome is made of a combination of any number of flags, with certain flags taking precedence over others:

Transaction is read-only only if it's heuristic decision is equal to READONLY
Transaction has made a commit decision only if it's heuristic decision is equal to COMMIT
Transaction has made a rollback decision only if it's heuristic decision is equal to ROLLBACK
Transaction has made a mixed decision if it's heuristic value has the MIXED flag set, or both the COMMIT and ROLLBACK flags set
Transaction has made a hazard decision if it's heuristic value has the HAZARD flag set

Version:: $Revision: 1.5 $ $Date: 2001/03/12 19:20:19 $
Author:: Assaf Arkin
See Also:: Transaction, TransactionImpl#normalize

Field Summary
`static int`	`COMMIT` Indicates that all resources in the transaction (at least one, excluding any read-only) have agreed to commit during the preparation stage and the transaction could be commited in its entirety.
`static int`	`HAZARD` Indicates that resources have commited, or resources have rolled back, but we don't know what was the exact outcome.
`static int`	`MIXED` Indicates that some resources have commited and others have rolledback, the transaction should be rolled back as much as possible, but could not definitely be rolled back.
`static int`	`OTHER` Indicates that an other type of heuristic response, not ReadOnly, Commit, Rollback, Mixed or Hazard, occurred during the transaction.
`static int`	`READONLY` Indicates that the transaction has no resources or has only read-only resources.
`static int`	`ROLLBACK` Indicates that one or more resources in the transaction (excluding read-only) could not be prepared or that an error marks this transaction as faulty.
`static int`	`TIMEOUT` Transaction has been timed out and has been rolled back.

Field Detail

READONLY

public static final int READONLY

Indicates that the transaction has no resources or has only read-only resources. A read-only transaction does not need to participate in the second phase.

See Also:: Constant Field Values

COMMIT

public static final int COMMIT

Indicates that all resources in the transaction (at least one, excluding any read-only) have agreed to commit during the preparation stage and the transaction could be commited in its entirety.

See Also:: Constant Field Values

ROLLBACK

public static final int ROLLBACK

Indicates that one or more resources in the transaction (excluding read-only) could not be prepared or that an error marks this transaction as faulty. The transaction should be rolled back in its entirety.

See Also:: Constant Field Values

MIXED

public static final int MIXED

Indicates that some resources have commited and others have rolledback, the transaction should be rolled back as much as possible, but could not definitely be rolled back.