HP 3000 Manuals HP 3000 Manuals
Chapter 7 Logging and Recovery
This chapter discusses how to maintain database consistency; that is, how
to log logical transactions and recover a TurboIMAGE/XL database from a
system failure or program abort. This chapter is divided into the
following major sections:
* Recovery Options
* Logical Transactions
* Dynamic Roll-Back Recovery
* Intrinsic Level Recovery
* Logging Preparation
* Logging Status
* Logging Maintenance
* Roll-Forward Recovery
* Roll-Back Recovery
* DBRECOV Commands Used With Roll-Forward and Roll-Back Recovery
* Record Tables
* Post-Recovery Options
* Mirror Database Using DBRECOV
A quick guide to recovery and logging options is found in appendix G,
"Recovery and Logging Quick Reference."
Database Utilities Used in Logging and Recovery
The TurboIMAGE/XL database is maintained using various TurboIMAGE/XL
database utilities which are fully described in chapter 8. Because the
following database utilities are used in logging and recovery, they are
also referred to in this chapter:
DBUTIL Creates and maintains the database.
DBUNLOAD Copies data to specially formatted tape volumes.
DBLOAD Loads data from backup volumes (DBUNLOAD tape) into
the database.
DBSTORE Stores a database to tape.
DBRESTOR Restores a database from backup volumes (DBSTORE
tape) to disk.
DBRECOV Recovers a database from a log file. The DBRECOV
utility allows you to set control commands and
create individual user recovery files. The
information from these files enables you to inform
each user where to resume transactions within the
database.
Database utilities can be run in either job or session mode. With the
exception of the DBUTIL >>SHOW command, the utilities DBUTIL, DBSTORE,
DBRESTOR, DBUNLOAD, and DBLOAD all require a logon in the group and
account that contains the database root file. Consequently, these
utilities cannot be used with a remote database unless you initiate a
remote session and run the utility as part of that session. The DBUTIL,
DBSTORE, and DBRESTOR utilities do not allow you to use the MPE/iX FILE
command to equate a database or database-access file.
CAUTION DBUNLOAD and DBLOAD do allow MPE/iX FILE commands to equate a
database and can redirect the database to a different file.
Except in a controlled environment, you should not use the
MPE/iX FILE command to redirect a database or database-access
file to a different file because that file can be purged easily.
The DBRECOV utility is not included in the discussion above because it is
an exception. With DBRECOV, MPE/iX FILE commands are permissible and do
not require a logon to the same group and account as the log file.
However, DBRECOV must be invoked on the system where the database
resides.
You can operate the database utilities if you are the database creator or
if you know the maintenance word. If no maintenance word is defined,
only the database creator can execute the database utilities. The
exception to this rule is that a user with system manager (SM) capability
can use the DBUTIL >>SHOW command on any database without having to
supply the maintenance word.
Use this chapter together with chapter 8 which gives the syntax of the
database utilities and commands.