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  1. #1
    Join Date
    Jul 2006
    Posts
    13

    Unanswered: About worker processes

    What's the role of worker processes?
    Only for parallel query? if I set max parallel degree = 1, then the DBMS will not perform parallel query, will worker processes be invoked then?
    Thanks very much...

  2. #2
    Join Date
    Sep 2002
    Location
    Sydney, Australia
    Posts
    255
    What's the role of worker processes? Only for parallel query?
    For the purposes of your use and understanding, YES. But parallelism has been implemented across the board, for internal facilities that would benefit so, NO.

    if I set max parallel degree = 1, then the DBMS will not perform parallel query
    Yes
    will worker processes be invoked then?
    Yes. Worker processes are the additional layer, implemented for parallelism, so you cannot do without them, you can only reduce them to 1, but do not do so.

    Setting max_parallel_degree to 1 essentially turns parallelism off. This is the default setting, so if it is not 1, someone has turned parallelism on ... so you may not want to turn it off.

    Note, there are several (SAG Ch 4, P&TG Ch 8) config parms ("*worker processes*") that deal with parallelism and worker processes. They interact with each other, you should consider them togther, not change just one. Given your question, I recommend that you do not change the default config values, do not try to limit resources used for parallelism, including worker processes; you will end up strangling the server. Read the manuals before changing config parms.

    Cheers
    Derek Asirvadem
    Senior Sybase DBA/Information Architect derekATsoftwaregemsDOTcomDOTau
    Anything worth doing is worth doing Right The First Time
    Spend your money on standards-compliant development or spend 10 times more fixing it

  3. #3
    Join Date
    Jul 2006
    Posts
    13
    Thanks

    But would you confirm below question?
    If max parallel degree = 1(no parallelism), will worker process be invoked?

  4. #4
    Join Date
    Jul 2006
    Posts
    13
    the default value of number of worker processes is 0.
    I think worker processes are invoked for parallel query only,if there's no parallel query, work processes will not be invoked at all, even for normal query, am I right ?

  5. #5
    Join Date
    Jan 2003
    Location
    Geneva, Switzerland
    Posts
    353
    Worker processes won't be invoked for queries, but they can be used in other circumstances, such as dbcc checkstorage.

    Michael

  6. #6
    Join Date
    Sep 2002
    Location
    Sydney, Australia
    Posts
    255
    What does it matter ? It looks like you are trying to tune performance without understanding the resources and interdepence. Smells like danger and someone is going to get blamed. Do NOT mess with the config unless you know what you are doing.

    From the ASE 12..5.1 SAG:
    number of worker processes specifies the maximum number of worker processes that Adaptive Server can use at any one time for all simultaneously running parallel queries combined.
    From memory, the default of zero just means "use whatever I need" from the several config parms related to parallelism. There is a diagram in p136 of the SAG (PDF version) that may help. Don't forget the Dynamic/Static and actual Run values of the config parms.

    If max parallel degree = 1(no parallelism), will worker process be invoked?
    Yes, there will be one worker process (operating minimum being one nto zero). The rule of thumb is:
    number of worker processes should be set to max number of partitions plus one. Partitions (parallelism) is one for you therefore NOWP should be a minimum of two for you. It is a tiny memory resource, like user connections, so without knowing much about your system, I would recommend a minimum of five. Set the memory per worker process to 2048.

    Don't forget, parallelism is not just for queries, ASE has parallel bcp, parallel dbcc, parallel sorts (for index builds and order-by). If you try to remove parallel ism, you will be putting the server in a pre-11.5 state, and worse.
    Derek Asirvadem
    Senior Sybase DBA/Information Architect derekATsoftwaregemsDOTcomDOTau
    Anything worth doing is worth doing Right The First Time
    Spend your money on standards-compliant development or spend 10 times more fixing it

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