Re: x$ constructs and memory

Hi Steve,

Thank you for your explanation, but I got few additional questions ig you got a chance to answer:

> (There are similar X$ interfaces for other memory heaps). As you may know,
> heaps are implemented as a heap descriptor and linked list of extents, and
> within each extent there is a linked list of chunks. So what is done is
that

Is there a linked list for *all* chunks in a heap as well, regardless of their type, or is there only a list for each type of chunks, free and recreatable ones?
Am I correct that permanent chunks don't have to be in any list because they're never deallocated and they should stay in same place anyway?

> Some "X$ tables" have become "X$ interfaces" in recent versions, for
example
> X$KTCXB and X$KSQRS. These correspond to the transactions and enqueue
> resources arrays respectively. The reason is that they are no longer fixed
> arrays. Instead they are "segmented arrays" that can be dynamically
extended
> by adding discontiguous chunks of shared pool memory to the array. The
> freelists and latching for these arrays in unchanged however. All you will
> notice is that the ADDR column of the X$ output now returns addresses
which
> map into your PGA rather than the SGA. In fact, that is in general a good
> way to work out whether you are looking at an X$ table or an X$ interface.

I've noticed that some tables such x$ktcxb and x$kturd return the same ADDR value for all it's rows. I've always thought, that it means a subroutine or function is returning the results instead of a direct read from array, as you described. But x$ksqrs does return different ADDRs for each row (9.2.0.4 on W2K). Am I on wrong tracks here?

Thank you!
Tanel.

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Author: Tanel Poder
  INET: tanel.poder.003_at_mail.ee

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