DB2 Version 9.7 for Linux, UNIX, and Windows

LIST INDOUBT TRANSACTIONS command

Provides a list of transactions that are indoubt. The user can interactively commit, roll back, or forget the indoubt transactions.

The two-phase commit protocol comprises:

The PREPARE phase, in which the resource manager writes the log pages to disk, so that it can respond to either a COMMIT or a ROLLBACK primitive
The COMMIT (or ROLLBACK) phase, in which the transaction is actually committed or rolled back.

Forgetting a transaction releases resources held by a heuristically completed transaction (that is, one that has been committed or rolled back heuristically). An indoubt transaction is one which has been prepared, but not yet committed or rolled back.

Scope

This command returns a list of indoubt transactions on the executed node.

Authorization

None

Required connection

Database. If implicit connect is enabled, a connection to the default database is established.

Command syntax


>>-LIST INDOUBT TRANSACTIONS--+----------------+---------------><
                              '-WITH PROMPTING-'

Command parameters

WITH PROMPTING

Indicates that indoubt transactions are to be processed. If this parameter is specified, an interactive dialog mode is initiated, permitting the user to commit, roll back, or forget indoubt transactions. If this parameter is not specified, indoubt transactions are written to the standard output device, and the interactive dialog mode is not initiated.

Interactive dialog mode permits the user to:

List all indoubt transactions (enter l)
List indoubt transaction number x (enter l, followed by a valid transaction number)
Quit (enter q)
Commit transaction number x (enter c, followed by a valid transaction number)
Roll back transaction number x (enter r, followed by a valid transaction number)
Forget transaction number x (enter f, followed by a valid transaction number).

A blank space must separate the command letter from its argument.

Before a transaction is committed, rolled back, or forgotten, the transaction data is displayed, and the user is asked to confirm the action.

The LIST INDOUBT TRANSACTIONS command returns type information to show the role of the database in each indoubt transaction:

TM: Indicates the indoubt transaction is using the database as a transaction manager database.
RM: Indicates the indoubt transaction is using the database as a resource manager, meaning that it is one of the databases participating in the transaction, but is not the transaction manager database.

Usage notes

An indoubt transaction is a global transaction that was left in an indoubt state. This occurs when either the Transaction Manager (TM) or at least one Resource Manager (RM) becomes unavailable after successfully completing the first phase (that is, the PREPARE phase) of the two-phase commit protocol. The RMs do not know whether to commit or to roll back their branch of the transaction until the TM can consolidate its own log with the indoubt status information from the RMs when they again become available. An indoubt transaction can also exist in an MPP environment.

If LIST INDOUBT TRANSACTIONS is issued against the currently connected database, the command returns the information on indoubt transactions in that database.

Only transactions whose status is indoubt (i), or missing commit acknowledgment (m), or missing federated commit acknowledgment (d) can be committed.

Only transactions whose status is indoubt (i), missing federated rollback acknowledgment (b), or ended (e) can be rolled back.

Only transactions whose status is committed (c), rolled back (r), missing federated commit acknowledgment (d), or missing federated rollback acknowledgment (b) can be forgotten.

In the commit phase of a two-phase commit, the coordinator node waits for commit acknowledgments. If one or more nodes do not reply (for example, because of node failure), the transaction is placed in missing commit acknowledgment state.

Indoubt transaction information is valid only at the time that the command is issued. Once in interactive dialog mode, transaction status might change because of external activities. If this happens, and an attempt is made to process an indoubt transaction which is no longer in an appropriate state, an error message is displayed.

After this type of error occurs, the user should quit (q) the interactive dialog and reissue the LIST INDOUBT TRANSACTIONS WITH PROMPTING command to refresh the information shown.