System Management Guide: Communications and Networks

TTY Troubleshooting

This section discusses troubleshooting the tty subsystem:

The system records the number of getty processes spawned for a particular tty in a short time period. If the number of getty processes spawned in this time frame exceeds five, then the Respawning Too Rapidly error is displayed on the console and the port is disabled by the system.

The tty stays disabled for about 19 minutes or until the system administrator enables the port again. At the end of the 19 minutes, the system automatically enables the port, resulting in the spawning of a new getty process.

Possible Causes

Procedures for Recovery

Correct modem configuration:
Ensure that the modem carrier detect is not forced high.

Note: The following applies to Hayes-compatible modems.
1. Connect to the modem and examine the active profile.
2. Set the modem carrier detect to &C1 rather than &C0 (forced high). Use the following AT modem commands to set and change the carrier attribute:
```
AT&C1
AT&W
```
  Notes:
  1. See Sending AT Commands with the cu Command
  2. See your modem documentation for further information.
Disable the tty, remove the tty definition, or attach a device to the port:
- To disable the tty definition use the chdev command as follows:
```
chdev -l ttyName -a Login=disable
```
  After running this command, the tty does not become enabled after a system restart.
- To remove the tty definition:
  1. Disable the tty port, use the pdisable command, enter:
```
pdisable ttyName
```
  2. Remove the tty definition from the system. See Managing TTY Devices for further information.
Check for bad cables or loose connections:
1. Check cabling. Tighten loose connections and replace damaged or inappropriate connectors.
2. Verify that the suspected cabling is IBM serial cable P/N 6323741 or that the cable meets the same standard. Replace damaged or inappropriate cables.
Eliminate noise on communication line:
1. Verify that cabling is correct length and impedance.
2. Ensure that toroid rings are in place where needed on longer cables.
3. Check routing of cables; they should not be close to fluorescent lights or motors.
Check for corruption of, or tampering with, the /etc/environment or the/etc/inittab files:
1. If possible, compare these files against known good copies.
2. Copy the files as a backup and make changes as needed.
3. In the /etc/environment file, remove any lines that are not:
  - blank lines
  - comment lines
  - variable=value
4. In the /etc/inittab file, examine the tty devices lines. If the tty is set to off, it is likely that the tty port is not being used. If it is not being used, remove the tty definition or attach a device to the port.
Remove corrupted tty configuration:
1. Remove the tty definition. Use the Web-based System Manager Devices application or see Managing TTY Devices for further information.
2. If you want a hard copy record of the tty definition before removing it, press the Image key (F8 or Esc+8). This will capture the current screen image and copy it to the smit.log file in your $HOME directory.
3. Read the tty definition. See the instructions for Adding a TTY under Managing TTY Devices.
Locate defective hardware:
1. Run diagnostics using the diag command.
2. If any hardware problems are detected, follow local problem solving procedures.

Error Log Information and TTY Log Identifiers

The following sections discuss important error logging files and commands and common error report messages relating to ttys.

Important Error Logging Files and Commands

Command: errclear

This command deletes entries from the error log. The entire log can be erased with errclear 0 or entries with specified error ID numbers, classes, or types can be removed.

Command: errpt

This command generates an error report from entries in the system error log. The most used format for this command is errpt -a | pg, which generates a detailed report starting with the most current errors.

File: /var/adm/ras/errlog

This file stores instances of errors and failures encountered by system. The errlog file tends to become quite lengthy. If not cleared on a regular basis, it can occupy quite a bit of space on your hard disk. Use the errclear command mentioned previously to clean out this file.

File: /usr/include/sys/errids.h

The errids.h header file correlates error IDs with error labels.

Common Error Report Messages

Message	Description	Comments
Core Dump	Software program abnormally terminated	This error is logged when a software program abnormally ends and causes a core dump. Users might not be exiting applications correctly, the system might have been shut down while users were working in application, or the user's terminal might have locked up and the application stopped.
Errlog On	Errdaemon turned on	This error is logged by the error daemon when the error logging is started. The system automatically turns off error logging during shutdown.
Lion Box Died	Lost communication with 64-port concentrator	This error is logged by the 64-port concentrator driver if communications with the concentrator are lost. If you receive this error, check the date and time stamp to see if user might have caused this message to occur. A series of these errors can indicate a problem with the 64-port adapter or its associated hardware.
Lion Buffero	Buffer overrun: 64-port concentrator	This error occurs when the hardware buffer in a 64-port concentrator is overrun. If device and cabling allow, try adding request to send (RTS) handshaking to the port and device. Also try lowering the baud rate.
Lion Chunknumc	Bad chunk count: 64-port controller	This error occurs when the value for the number of characters in a chunk does not match the actual values in the buffer. This error may indicate a problem with the hardware; try running diagnostics on devices.
Lion Hrdwre	Cannot access memory on 64-port controller	This error is logged by the 64-port concentrator driver if it is unable to access memory on the 64-port controller.
Lion Mem ADAP	Cannot allocate memory: ADAP structure	This error is logged by the 64-port concentrator driver if the malloc routine for the adap structure fails.
Lion Mem List	Cannot allocate memory: TTYP_T List	This error is logged by the 64-port concentrator driver if the malloc routine for the ttyp_t list structure fails
Lion Pin ADAP	Cannot pin memory: ADAP structure	This error is logged by the 64-port concentrator driver if the pin routine for the adap structure fails.
SRC	Software program error	This error is logged by the System Resource Controller (SRC) daemon in the event of some abnormal condition. Abnormal conditions are divided in three areas: failing subsystems, communication failures, and other failures.
Lion Unkchunk	Unknown error code from the 64-port concentrator	Error Code: Number of characters in the chunk received.
TTY Badinput	Bad ttyinput return	Error Code: System error code (see sys/errno.h). This is logged by the tty driver if ttyinput routine returns an error.
TTY Overrun	Receiver overrun on input	The sending device is ignoring flow control and overloading the hardware buffer on the adapter. This occurs before the driver accesses the hardware FIFO. Try adding `rts` handshaking to the port and to device (if possible).
TTY TTYHOG	TTYHOG overrun	The sending device is ignoring flow control. This error occurs after the hardware first in/first out (FIFO) has been accessed and has written to the software buffer. In other words, the tty hog error is logged because the buffer in which incoming characters are placed is overflowing. When the buffer is about three-fourths full, the device driver notifies the hardware (in this case, tty) to send the XOFF char to the sender to stop sending data. If the sender continues to send data and the buffer is not emptied, the device driver flushes the buffer and logs the error message in the error log.
TTY Parerr	Parity/Framing error on input	This error indicates parity errors on incoming data to asynchronous ports on a character-by-character basis.
TTY Prog PTR	Software error: T_HPTR field invalid	This error is logged by the tty driver if t_hptr pointer is null.