When updates to CDB values take effect for VTAM (SNA) connections

Any table in the CDB can be updated while DDF is active.

The changes take effect as follows:

  • Updates to LUMODES take effect the next time DDF is started, or on the initial session to a given LUMODE combination.
  • Updates to LUNAMES, LOCATIONS, and LULIST take effect as follows:
    • If DDF has not yet tried to communicate with a particular remote location, rows added to LUNAMES and LOCATIONS take effect when DDF attempts to communicate with that location.
    • If DDF has already attempted communication with a particular location, rows added to LUNAMES and LOCATIONS take effect the next time DDF is started.
  • Updates to USERNAMES and MODESELECT take effect at the next thread access.
  • Deletion of rows from any CDB table takes effect the next time DDF is started.

In all cases, existing conversations continue to operate as the table specified before the update.

Recommendation: If you are switching from TCP/IP to VTAM connections, stop and start DDF after you modify the CDB tables.
Important: The process of modifying the CDB, particularly MODESELECT and USERNAMES, can interfere with DDF access to the tables. This could potentially cause deadlocks and timeouts, which cause the attempted access to the remote system to fail.