Windows onlyAlternative Hosts

An Alternative Host List entry allows the user to specify a set of Alternative Hosts to cater for situations when hosts are inaccessible or down. If the connection to the first host fails, then the next host in the list is tried, and so on. The entry consists of a list of Destination Host entries in the order in which connection attempts are to be made. There is no limit to the number of Destination Hosts; however, the combined length of the host names plus the number of names cannot exceed 256.

Failed hosts are marked as failed until a timeout period expires; subsequent connections to the Destination Host entry will not try any hosts that are marked as failed. If none of the connections succeeds, an error message is displayed. The failed hosts will then be re-enabled and the next connection attempt will start again at the beginning of the list.

An Alternative Host List entry contains the following information:

Entry name The name of the entry.

Alternatives list A list of Destination Host entry names.

Back off A list of timeout values - one for each host in the Alternatives list. A timeout value is the length of time (in seconds) during which connection to the destination system will not be re-attempted once a connection attempt has failed. A suitable initial value is 300 seconds (5 minutes).

netadmin option 2 - Alternative Host Lists  allows you to add, delete, edit and list Alternative Host List entries. Selecting this option displays the menu:

Northgate NETWORK ADMINISTRATION - ALTERNATIVE HOST LISTS
1. Add alternative host list
2. Edit alternative host list
3. Delete alternative host list
4. List alternative host lists
Select action [1-4 / q]:

Adding an Entry

To add an Alternative Host List entry, select option 1 from the Alternative Host Lists menu. The following sequence of prompts is displayed.

  1. Enter alternative host list name [AlternativeListName / q] :
     >>

    Enter the name by which the Alternative Host List entry is to be known. If the name is already in use, you are re-prompted. The name must be no longer than 49 characters.

  2. The names of the existing Destination Host entries are displayed and you are prompted to enter the entry number of a host to add to the list. If there are more than 20 entries, press return to display the next list.

    If your list of Alternative Hosts is complete, enter x to exit - go to step 4.

  3. You are then prompted for a backoff timeout value for the host you have just selected. Enter the required value in seconds or press return to select the default (0 seconds - retry immediately).

    Return to step 2.

  4. The complete Alternative Host List entry is displayed, followed by a confirmation prompt. Enter y  to save the entry, or n  to discard it; you are then returned to the menu.

Editing an Entry

To edit an Alternative Host List entry, select option 2 from the Alternative Host Lists menu.

  1. The names of the existing entries are displayed - enter the number of the required entry. If there are more than 20 entries, press return to display the next list.

  2. The contents of the selected list are displayed, followed by a prompt that allows you to change the list name - enter a new name if required or press RETURN to retain the current name.

  3. You are then asked if you wish to change the list.

    • Enter y  to change the list. You must re-enter the complete list as described in Adding an Entry.

    • Enter n  to keep the same list of destination host names.

  4. The complete entry is displayed, followed by a confirmation prompt. Enter y  to save the entry, or n  to discard your changes; you are then returned to the menu.

Deleting an Entry

To delete an Alternative Host List entry, select option 3 from the Alternative Host Lists menu.

  1. The names of the existing Alternative Host List entries are displayed and you are prompted to enter an entry number. If there are more than 20 entries, press return to display the next list.

  2. The details of the selected entry are displayed, followed by a prompt asking you to confirm that you want to delete it. Enter y  to delete the entry, or n  to keep it; you are then returned to the menu.

Listing Entries

To list Alternative Host List entries, select option 4 from the Alternative Host Lists menu.

  1. The names of the existing Alternative Host List entries are displayed and you are prompted to enter an entry number or *  to list the details of all the entries. If there are more than 20 entries, press return to display the next list.

  2. The details of the selected list are displayed. Press RETURN after each entry to display the next one, or enter q  to return to the menu. At the end of the list you are returned to the menu.