Re: [PDO] Question on Persistent PDO Connections

Christopher Jones wrote:
>  > Just to clarify terms here - what are you referring to by 'session'?
> 
> Here session refers to the resources used by the PHP connection. In
> OCI8, session & connection are pretty much synonymous.  But if you had
> a multi-threaded mid-tier you could code an application to have
> multiple user sessions per physical DB connection.  Fundamentally it's
> a way of resource sharing. The connection is a "pipe" to the DB and
> the session is the work being done across the pipe.
> 
>  > I would not expect transactions to remain open from one page load to
>  > the next, but that seems to be what some people are asking for?
>  > Anything that needs to be persistent across page loads should be
>  > held either in the database or outside transactions?
>  >
>  > One can not run a multiuser system if someone is going to start a
>  > transaction but not finish it - perhaps due to loss of connection ....
> 
> Transaction monitors traditionally allow external control of
> transaction state.  In Oracle 11g this has been exposed through to a
> simple API which is fun: a DB transaction can span multiple HTTP
> requests. See
> http://download.oracle.com/docs/cd/E11882_01/appdev.112/e10471/adfns_xa.htm#ADFNS802 

What happens in this example where the suspended transaction is never 
completed? Sounds like a recipe for disaster to me ;)

Once a transaction is opened in Firebird, the MGA (Multi Generational 
Architecture) maintains a snapshot of the current state of records. 
Changes by other transactions can only be made if not blocked by other 
un-committed transactions, but everybody gets a clean view of the 
database. Holding transactions open maintains the view at the time the 
transaction was opened, and if not refreshed a some point, the 'last 
active transaction' counter does not advance. These means that long time 
running reports generate a clean set of results from that particular 
time - not broken by other activity on the database while the query was 
running.

SO suspending a transaction would cause a major bottleneck that may 
block the database at some point if not cleared :(

-- 
Lester Caine - G8HFL
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