iX V6.5 (30391-90011)

360 Chapter7

Logging and Recovery

DBRECOV Commands Used with Roll-Forward and Roll-Back Recovery

ROLLBACK Command

The >ROLLBACK command is used for roll-back recovery. It designates the name of a

database to be rolled back. Any incomplete transactions at the time of the system failure

are rolled out. Multiple databases may be roll-back recovered by entering more than one

database name after the command.

Conditions necessary for the success of the >ROLLBACK command include the following:

• The database must be accessible to you when running DBRECOV. If the database resides

in a group or account different from the your logon, the MPE/iX ﬁle security must

permit the user read and write access to the database ﬁles.

• The log identiﬁer characteristics (name, password, log ﬁle name, and device type) must

not have been altered since the log ﬁle was generated.

• The database must be enabled for recovery and roll-back.

• All databases speciﬁed for roll-back recovery must contain the same log identiﬁer.

• You must be the database creator, or know the database maintenance word.

• You must either be the creator of the log identiﬁer, or have system manager (SM) or

operator (OP) capability.

• No other users can be accessing the database when >ROLLBACK is called. The database

may be concurrently accessed by users when the >CONTROL command is speciﬁed with

the MODE4 option.

Note that the >ROLLBACK command itself does not initiate recovery, but makes several

preparatory checks. The recovery system is actually initiated by the >RUN command.

RUN Command

After the >RUN command is given, the DBRECOV program recovers the speciﬁed databases,

creates speciﬁed user recovery ﬁles, and terminates. The DBRECOV program could be

terminated alternatively without any recovery taking place with an >EXIT command.

For recovery to succeed, the person running DBRECOV (usually the database administrator)

must have access to the log ﬁle. This implies either knowing the maintenance word and

having system manager (SM) or operator (OP) capability or being the creator of the log

identiﬁer with read access to the log ﬁle if it resides on disk in a different logon group and

account. If the log ﬁle is on tape, the user must be able to provide the volume identiﬁer to

the operator mounting the tape.