Note again that account-restores are not recorded by the transaction logger.
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3.5.1 TRANSACTION LOGGING AND THE LOG COMMAND
The transaction logger is invoked by executing the 'LOG' command from TCL on the SYSPROG account. This causes the terminal to be dedicated to transaction logging. until the transaction logger is exited, the terminal remains dedicated to transaction logging and cannot be used for other purposes.
Ultimate recommends that the transaction-logging terminal be any terminal line other than line zero (0). This is because line 0 is considered a "system console" and is used to boot the system (warmstart and coldstart) and for other system functions.
Only one terminal can be used for transaction logging. If logging has already been started on another terminal, an error message is displayed and control returns back to TCL.
The dedicated terminal is used to display menus, status information, and error messages, and to get operator input.
The Transaction Logger Main Menu
After the transaction logger is invoked, the main menu (see Figure A) is displayed on the terminal screen.
Logger status: Inactive Transaction Logger
1. Activate logger; start tape 2. Deactivate logger; exit menu 3. Suspend tape
4. Restart tape
5. Change tape attachment parameters
Enter option or <CR> to display status:
Figure A. Transaction Logger Main Menu
Press <CR> to display the status of the logger (shown above).
The logger will be in one of three possible states:
Inactive
Active and started Active and suspended
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The Three possible states of the Transaction Logger
Once the transaction logger is invoked on a terminal, the logger may be in one of the three possible states:
1. Inactive - The logger is invoked on a terminal but is otherwise doing nothing.
2. Active and started - the logger is Active and is logging transactions. Also, the tape operation is started and transactions are being written to the tape.
3. Active and suspended - the logger is active and is logging transactions. However, the tape operation is suspended. Suspending tape allows the tape drive to be used temporarily for other purposes by
another port (e.g., T-DUMP or T-LOAD files).
During this time, transactions are recorded on disk. When tape operation is restarted for the transaction logger, these transactions are written out to tape.
Tape should not be suspended for any great length of time, since:
(1) if a failure occurs, the transactions queued up on disk but not written to tape cannot be
recovered;
(2) overflow frames are used to store the
transactions and if already low on disk space, the system may slow down and/or run out of disk space.
How the Transaction Logger Works
When an operator presses a key at the terminal in response to the 'Enter option:' prompt, the transaction logger menu
handler validates the input (a number from 1 to 5), performs the requested operation if possible, prints a response, and re-displays the current logger status and the main menu.
Whenever the logger is active, logging takes place in the background while the menu handler is waiting for input.
However, since the transaction logging and the menu handler share the same workspace (of the dedicated terminal), the transaction logging can not take place when the menu handler is busy taking options from the operator and/or displaying status and menu. Hence, use the terminal sparingly.
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A Transaction Logging Session
In order to allow the user to do FILE-SAVE's, T-DUMP's, or any other tape operations, the transaction logger can be suspended or deactivated to detach the tape drive from the logger.
A "transaction logging session" starts when the logger is activated or restarted and ends when the the logger is deactivated or the tape operation is suspended.
During a transaction logging session, more than one reel of tape may be needed to log all transactions. The system will display a message "Mount reel #n" to ask the operator to mount a new reel of tape. All reels of tape made in the same session are collectively called a "transaction session tape set".
Each new transaction logging session starts a new
"transaction session tape set". A new reel of tape should be mounted before a new session starts. In other words, before the transaction logger is to be activated or restarted, the operator should mount a new reel of tape and the tape must be at the BOT (Beginning Of Tape) mark. The transaction logger will write a "sequencing information segment" to the
beginning of the tape to signify the beginning of a new transaction logging session.
When the user deactivates the logger or suspends the tape operation, the transaction logger writes a tape End Of File
(EOF) mark to tape to signify the end of the transaction logging session.
Choosing Transaction Logger Menu Options The main menu options are shown below:
Transaction Logger
1. Activate logger; start tape 2. Deactivate logger; exit menu 3. Suspend tape
4. Restart tape
5. Change tape attachment parameters
Enter option or <CR> to display status:
Option
1:
This option activates the logger and starts the tape operation. A transaction tape must be already mounted on the tape drive and loaded at the BOT mark. This option starts a new transaction logging session. The logger writes af'sequencing information segment" to the beginning of the tape to signify the beginning of a new session.
If the tape drive is off line, an error message is displayed
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and the transaction logger remains Inactive. new transaction logging session, and each deactivation ends the current transaction logging session. During the period when the logger is inactive, system updates are not logged as transactions.
Before the logger is activated, a new reel of tape should be mounted. (In other words, each transaction logging session should start with a new reel of tape, loaded at the BOT possible. The transaction logger, at this time, is-active-Sut is waiting for the tape operation to continue.
Transactions are recorded on disk and overflow frames are used if needed. If a system failure~occurs before a second reel of tape can be mounted, transactions queued up on disk are lost.
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