Re: LMT concurrency

Waleed-

The main enqueue (lock) used during locally managed tablespace operations is the TS enqueue, particularly for segment create and drop operations. This is distinct from the ST enqueue, which serializes access to the uet$ and fet$ dictionary tables. The TS enqueue was originally created to implement temporary segment operations, but is used for LMT segment creation as well and allows concurrent processes to hold shared locks. The ST enqueue forced all extent and therefore segment operations to be serialized for the entire database (not just the instance!). With LMT and the TS enqueue, you can create multiple segments at the same time without enqueue contention.

Even within a tablespace, multiple segments can be created at once without enqueue contention, unlike the dictionary managed tablespaces. Other enqueues are used during extent creation, such as the TM and TX enqueues. What is important here is that the limit to concurrency we saw with dictionary managed tablespaces is gone with the LMT tablespaces.

• ricky

wkhedr wrote:
>
> Hi,
>
> Does anybody know what control structure (latch, lock, enqueue, etc.)
> is being used to control the concurrency of the processes allocating
> or accessing extents in Locally-managed tablespaces specially the
> files' headers that contain the extents bitmap?
>
> Regards,
>
> Waleed
Received on Sat Jun 30 2001 - 08:34:17 CDT