TurboIMAGE/XL Database Management System Reference Manual (30391-90012)

324 Chapter7
Logging and Recovery
Logging Preparation
Logging Preparation
User logging is required for roll-forward recovery, roll-back recovery, and to maintain a
mirror database. It is not required for dynamic roll-back recovery, but is recommended to
protect against a hard disk failure. To prepare a database for user logging, you must set a
log identifier (logid) into the database root file. The log identifier can be associated with an
existing log file, in which case you can begin with step 6 below if you know the log
identifier and password. Note that to recover a database using a log file, you must either be
the creator of the logid, or supply the maintenance word and have system manager (SM) or
operator (OP) capability.
Assuming you intend to create a new log identifier, you should take the following steps:
1. Check MPE/iX logging configuration.
2. Acquire logging capability.
3. Determine whether the log file will reside on tape or disk.
4. If logging to disk, build the log file.
5. Create the log identifier.
6. Set the log identifier into the database.
7. Set flags for the database backup copy.
8. Make a backup copy of the database. This step is required when using roll-forward
recovery and recommended (for protection in the event of a hard disk failure), but not
required, when using roll-back recovery.
This is a one-time procedure. The logging maintenance operations are performed on a
regular basis, perhaps daily (refer to "Logging Maintenance" later in this chapter).
Step 1--Checking MPE/iX Logging Configuration
It is recommended that you check the logging configuration for adequate capacity before
using the MPE/iX LOG command described later in this section. This precautionary step
can prevent the downtime required to reconfigure the logging capacity. You need to check
the number of user logging processes allowed on the system and the number of users that
can access a single user logging process. For information on setting up these numbers at
system startup time, refer to the System Operation and Resource Management Reference
Manual.
Step 2--Acquiring Logging Capability
You must have MPE/iX logging (LG) or operator (OP) capability to use the following
MPE/iX commands: GETLOG, RELLOG, ALTLOG, CHANGELOG, and LISTLOG. You must have
LG or OP capability also if you intend to open a database with logging enabled. Logging
capability is acquired through the MPE/iX system manager and account manager
commands.
First, the system manager provides the account logging capability by using the MPE/iX