Hello Experts ,
i know that there is a schudel to purge Syslog file to delete records older than 7 days . i'd like to now what the longest time i can keep syslog without affecting system preformace
It's not about the number of days.. it's rather the number of records / table size. And it's impossible to say this without a deep evaluation of your environment. Generally speaking it should not have any significant impact in your overal system performance.
Considering that you have some monitoring in place that enable you to compare after change this value, I'd recommend you to set it to the value you need and see how this affects your system. I bet that it won't affect it at all.
Another possibility is create a archive mechanism for it, the same as you would do for tickets records. This could be either online in a clone table or offline as unload or csv file...
Most important is understand what do you want and why do you want what you want (hahaha my english is getting worse and worse :) )