Is transaction ID unique for the life of a DB?

Hi All,

First a statement of what I believe to be true and then the question.

A transaction ID consists of the combination of the the USN (i.e. v$transaction.xidusn), slot (v$transaction.xidslot) and sequence number (v$transaction.xidsqn). I can use package DBA_TRANSACTION function LOCAL_TRANSACTION_ID to get a session's transaction ID (in dot delimited format), optionally having the function begin a transaction if one is not already started. From what I've read, it's my understanding that a transaction ID is unique.

Now comes the question. Is a transaction ID in fact quaranteed to be unique for the entire life of a database? I suppose that the root of the question boils down to how the sequence number part of the transaction ID is arrived at, since obviously the usn and slot won't be unique. I've rooted around quite a number of resources and have not been able to find any specific (or even vague, for that matter) information regarding how the sequence number is derived.

    David Received on Wed Feb 12 2003 - 09:28:21 CST