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### 4.13 Reusing connection related information

For faster initial connection times, TRAMP stores previous connection properties in a file specified by the variable `tramp-persistency-file-name`.

The default file name for `tramp-persistency-file-name` is: `~/.emacs.d/tramp`.

TRAMP reads this file during Emacs startup, and writes to it when exiting Emacs. Delete this file for TRAMP to recreate a new one on next Emacs startup.

Set `tramp-persistency-file-name` to `nil` to disable storing connections persistently.

To reuse connection information from the persistent list, TRAMP needs to uniquely identify every host. However in some cases, two different connections may result in the same persistent information. For example, connecting to a host using `ssh` and connecting to the same host through `sshd` on port 3001. Both access methods result in nearly identical persistent specifications `/ssh:localhost:` and `/ssh:localhost#3001:`.

Changing host names could avoid duplicates. One way is to add a `Host` section in `~/.ssh/config` (see Frequently Asked Questions). Another way is to apply multiple hops (see Multi-hops).

When TRAMP detects a change in the operating system version in a remote host (via the command `uname -sr`), it flushes all connection related information for that host and creates a new entry.