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

Chapter 7 341
Logging and Recovery
Logging Maintenance
CHANGELOG Capability
The MPE/iX CHANGELOG feature provides a continuous MPE/iX user logging process, with
the ability to change tape or disk log files when they reach capacity without stopping the
user logging process. User logging also keeps track of the order of the files in the log file
set. Parts of the CHANGELOG record contain the file set number (001-999) and the device
type of the file names in the record. In addition, there are records for the previous file in a
set, first file in a set, and current file in a set. This format allows recovery to always start
at the beginning of the file set (or at any point within the file set if the sequence number is
used), and reopen the log files on the same device type that they were created.
The user issuing the CHANGELOG command must be the creator of the logid. If the user
issuing CHANGELOG is not the creator of the logid, either LG or OP capability is required. If
the mirror database method (DBRECOV STOP/RESTART) is being used, CHANGELOG makes
logging without interruption on the primary system possible.
NOTE If the database needs to be recovered when you are using the MPE/iX
CHANGELOG feature, the DBRECOV recovery facility may start at the first log file
in the logging cycle (for example, LOGF001), or at a different point (for
example, LOGF013) if you used TurboSTORE/iX 7x24 True-Online Backup.
Keep this in mind when determining the length of your logging cycle. See
"Recovering the Database" later in this section for a sample scenario.
Syntax
:CHANGELOG
logid [;DEV= device ]
Parameters
logid is the name of the currently active logging process.
device is the class of the device of the new log file (DISC, TAPE). If the device
class specified is DISC, the file is created in the logid creator's logon group
and account.
Example
:CHANGELOG ORDERLOG; DEV=DISC
Note that the logid specified must be that of the currently active logging process. If the log
file is changed using ALTLOG, no linkage of the log file set is provided. A CHANGELOG
command can only be used on a logid set up with the GETLOG command. The CHANGELOG
command terminates if the logging process state is INACTIVE, INITIALIZING, or
RECOVERING. The command will also terminate if a CHANGELOG command is already
pending. The following message is displayed on $STDLIST:
INVALID STATE OF PROCESS
After issuing the CHANGELOG command, if the logid is valid, CHANGELOG records are posted