sybase access path 
Author Message
 sybase access path

For the clarity (hopefully !), assume the following:

1       a PowerBuilder application is executing a stored procedure
2       there is no  procedure cache  
3       physical objects such as columns and indexes are
        not being added or deleted
4       the data distribution will change dramatically
5       the stored procedure uses variables, and their range of values
        can change dramatically from 1 execution to another
6       no re-compile options being used

Q -     Does SYBASE determine what the access path is when the DBA
        compiles the stored procedure, and it remains that way until
        the DBA physically re-compiles it again?
                                OR
        Can SYBASE dynamically ( at execution time ) determine what
        access path to use?



Mon, 21 Jul 1997 22:33:01 GMT
 sybase access path


Quote:

>For the clarity (hopefully !), assume the following:

>1   a PowerBuilder application is executing a stored procedure
>2   there is no  procedure cache  

    Then the procedure won't run.  I don't understand what this is meant
to simplify.

Quote:
>3   physical objects such as columns and indexes are
>        not being added or deleted
>4   the data distribution will change dramatically
>5   the stored procedure uses variables, and their range of values
>        can change dramatically from 1 execution to another
>6   no re-compile options being used

>Q - Does SYBASE determine what the access path is when the DBA
>        compiles the stored procedure, and it remains that way until
>        the DBA physically re-compiles it again?
>                            OR
>    Can SYBASE dynamically ( at execution time ) determine what
>        access path to use?

    If by access path you mean the order in which the tables are accessed and
which indexes are used (what Sybase calls the query plan), this is stored
in procedure cache when the SP is first executed and stays there until it is
flushed out of procedure cache by being least-recently-used.

    Additional, possibly different query plans can be generated and loaded
into memory by executing the SP WITH RECOMPILE, or if two users try to run
the SP at the same time.  But once a query plan is in memory it doesn't change,
even if it is grossly inappropriate for some later execution.

    Did I understand the question?

--
| Peter A. Lynn      |  "The only thing necessary for the triumph of evil  |

|     My opinions are my own, and may not reflect those of my employer (or |
| anyone else, for that matter.)  I reserve the right to change my mind.   |



Mon, 21 Jul 1997 23:06:02 GMT
 
 [ 2 post ] 

 Relevant Pages 

1. Accessing an Access Databse via a UNC path in VB6

2. Sybase bcp: wrong path separator

3. Replmerg uses a unc path when an ftp path has been specified

4. Replmerg uses UNC path despite explicit use of ftp path

5. Paths and App.Path

6. app-path and mdb-path

7. Getting Long File Path from short Path / File Name

8. A local DDF path and a remote Data path does not work on SP3 (NT)

9. Access 2.0 paths and attached tables

10. path to Access file is lost during scheduled DTS import

11. Runtime error 75 path/file access error

12. Access denied: XP_CMDSHELL and UNC paths


 
Powered by phpBB® Forum Software