Write ahead log

Database
Enthusiast

Write ahead log

Hi,

I know that WAL has redo records that need to be written to disks and has TJ recs . I am interested in the location,format and structure of its content. Can anyone please provide me the content or structure of this. The reason I am asking is that I saw while reading the doc,  WAL is protecting permanent tables and system tables.  I also see that WAL does not protect TJ tables, gtt, user journal tables. I am interested to know

1) If WAL does not protect TJ, which utility is responsible for its protection, can I say it is TD system?

2) I know TJ,Down-amp recovery journal and Permanent journal. I am not aware of User journal. This is new to me.

Your help is appreciated.

Thanks and regards,

Raja