Tail is a Unix command. Unix commands, unless specially formulated to work with z/OS files, don't tend to do well with z/OS files. CA-7 logs are z/OS files. I strongly suspect you will find that tail does nothing with the CA-7 log files. And yes, there are a primary and secondary log file so CA-7 can dump one while using the other one so merely using tail on one file, even if it worked, still loses you half the data.
i need to get all events in the ca7 like: job start, job end, job abend, force complete and so on.
What is so special about your site that it cannot do what all the other CA-7 sites do and use the montioring screens already a part of CA-7 to monitor jobs?
The format of the CA-7 log files is proprietary to CA and I doubt you will be able to get any information about their format from CA or anywhere else. CA writes a maximum of 2100 bytes per line, so you'll need to plan on spending a while to decipher the various fields. And if CA finds out you are doing so, they may well call this reverse engineering and they could pull your site license for CA-7 (and possibly all other CA products, depending upon your site agreement with CA). Your site may want to get permission from CA before going much further with whatever project you think you've been assigned to do, to prevent license issues.