Global Catalog and Local Catalog

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Fred
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Global Catalog and Local Catalog

Post by Fred » Tue Sep 22, 2015 10:18 pm

Hi,

When I was going through Vertica documentation, I came across a column called OBJECT_NAME in the system table LOCK_USAGE and the description of the column says "Name of object being locked; can be a table or an internal structure (projection, global catalog, or local catalog)." Can someone throw some insight as to what all constitutes global catalog and local catalog?

Thanks,Fred

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JimKnicely
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Re: Global Catalog and Local Catalog

Post by JimKnicely » Wed Sep 23, 2015 5:05 pm

Global Catalog Locks = Meta-data global across all nodes
  • 1. A GCL X lock is required for the following operations:
    • DDL Implicit Commit
    • DML Explicit Commit
    • Refresh
    • Recovery
    • Segment Balancing
    • Inviting a node to join the cluster
    2. These GCL operations block other GCL operations requiring locks
Local Catalog Locks = Meta-data local to a node
  • 1. A LCL X lock is required for the following operations:
    • DDL Implicit Commit
    • DML Explicit Commit
    • Moveout
    • Mergeout
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Fred
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Re: Global Catalog and Local Catalog

Post by Fred » Wed Sep 23, 2015 7:55 pm

Hi Jim,

Thanks for your time. A couple of clarifications though.

1. Did you mean to say "DDL IMPLICIT COMMIT" and "DML EXPLICIT COMMIT"? as DDL is always IMPLICITILY commited?
2. Why does DML commit need to acquire a GCLX? Is it because thats when AHM advances? which is a global entity?

Thanks, Fred.
Last edited by Fred on Thu Sep 24, 2015 12:33 am, edited 1 time in total.

NorbertKrupa
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Re: Global Catalog and Local Catalog

Post by NorbertKrupa » Wed Sep 23, 2015 9:04 pm

Fred wrote:2. Why does DML commit needs to acquire a GCLX? Is it because thats when AHM advances? which is a global entity?
My guess is because it's across all nodes.
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Re: Global Catalog and Local Catalog

Post by Fred » Thu Sep 24, 2015 12:37 am

Thanks Norbert. That makes sense. Also, AHM need not advance at the time of commit itself as I understand AHM advance depends on the Epoch management parameters.

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Re: Global Catalog and Local Catalog

Post by NorbertKrupa » Thu Sep 24, 2015 12:44 am

Fred wrote:Thanks Norbert. That makes sense. Also, AHM need not advance at the time of commit itself as I understand AHM advance depends on the Epoch management parameters.
Take a look at my StackExchange answer on AHM.
Checkout vertica.tips for more Vertica resources.

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