Specifications

2 IBM System z Personal Development Tool: Volume 3 Additional Topics

1.1 Token dates and times

The 1090 and 1091 tokens remember the latest date and time that it sees from the underlying

Linux system. It uses the Linux “software clock” for this purpose, without any time zone

adjustment. The token must never see the date or time move backwards. If this happens, a

time cheat message is produced and zPDT does not start.

For example, if you set the PC date ahead several months (perhaps to test an expiration

function in the application you are developing) and you use zPDT with this advanced date,

you cannot then return to the correct date and use the same token. If you inadvertently used

an incorrect (future) date with the token, and you now find the token unusable with the correct

date, you should contact the business partner that furnished the token.

If you must temporarily change the PC clock (when not using zPDT), remove the token

before doing this and reset the clock to the current time before connecting the token again.

If you move a token among multiple PCs, you should take care that the hardware time-of-day

clocks are close to each other on all the machines.

The settod command provided with zPDT provides a way to test software using different

dates; this does not change the value of the PC hardware clock or the Linux software clock.

A network time server can create problems for zPDT if it causes the Linux TOD to appear to

move backwards. (This is more likely to happen over a span of several boots and zPDT runs.)

When Linux first starts, it sets the Linux TOD clock (“software clock”) from the BIOS clock.

Later attempted synchronization with a network time server might cause this software clock to

move slower than the BIOS clock. If the zPDT token is connected it will record this time, which

is behind the BIOS clock. A subsequent boot and token connection may then see a

“backwards” time and this produces the “time cheat” messages that cause zPDT to stop.The

circumstances that create a time cheat problem are fairly rare and this should not be a

problem for most users.

PC BIOS clocks sometimes are not all that accurate, especially when a lot of heavy

processing is taking place. It might be a good idea to check your BIOS TOD (doing this during

PC startup, not under Linux).

1.2 crontab entries

zPDT places entries in the Linux cron tables, at root level. You can see these as follows:

$ su (change to root)

# crontab -l (list crontab entries for root)

@reboot /usr/z1090/bin/safenet_daemons_restart reboot > /dev/null

*/11 * * * * /usr/z1090/bin/safenet_daemons_restart > /dev/null

# exit (leave root)

Do not change or delete these entries. You may use cron functions for other purposes.

This is a technical statement. Your zPDT license agreement may restrict this usage.