Re: Latch process in Shared pool

On 2 Mar 2006 07:47:23 -0800, "Chintu" <agarwalp_at_eeism.com> wrote:

>Can someone please explain or point out links to the latch process in
>shared pool. What I have understood so far is the steps are as follows:
>1. In the process of searching a SQL text,
> It will first get data dictionary latch,
> do syntax check,
> If syntax is fine then release the latch ( Not sure about this one)
>2. Then get a library cache latch,
>check whether the the statement is already present,
>if the statement is already present, gets the execution plan and
>executes it
>Question : does it needs a shared pool latch here ??
>
>if the statement is not present ,
>latches the shared pool,
>allocates memory in shared pool and generates execution plans.
>
>I am very confused on this latch and parsing process. Kindly help !!
>
>Thanks
>Chintu.

The *algorithm* (not process) is completely different 1 compute the hash value of the statement 2 the hash value is being used to determine which part of the shared pool needs to be latched
3 find the statement
4 if is not present hard-parse the statement which means

• syntax and lexical check
• privilege check
• optimizer 5 if it is present no syntax and lexical check privilege check and optimizer as usual 6 release the latch.

--
Sybrand Bakker, Senior Oracle DBA