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Implementation of a Global Latch in a Multisystem Environment

IP.com Disclosure Number: IPCOM000112725D
Original Publication Date: 1994-Jun-01
Included in the Prior Art Database: 2005-Mar-27
Document File: 2 page(s) / 60K

Publishing Venue

IBM

Related People

Mohan, C: AUTHOR [+2]

Abstract

+-----------------------------------------------------------------+ | Latch Global latch | +-----------------------------------------------------------------+ | Requested State | Local Latch and Global Lock Operations | | | | | S | Acq. S local latch for the process | | | Acq. S lock if not held by the DBMS | | | | | X | Acq. X local latch for the process | | | Acq./Upg. X lock if not held by the DBMS| +-----------------------------------------------------------------+

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 51% of the total text.

Implementation of a Global Latch in a Multisystem Environment

+-----------------------------------------------------------------+
| Latch Global latch                                              |
+-----------------------------------------------------------------+
|   Requested State   |   Local Latch and Global Lock Operations  |
|                     |                                           |
|     S               |   Acq.  S local latch for the process     |
|                     |   Acq.  S lock if not held by the DBMS    |
|                     |                                           |
|     X               |   Acq.  X local latch for the process     |
|                     |   Acq./Upg. X lock if not held by the DBMS|
+-----------------------------------------------------------------+

+-----------------------------------------------------------------+
| Unlatch Global latch
|
+-----------------------------------------------------------------+
|   Held State        |   Local Latch and Global Lock Operations  |
|                     |                                           |
|     S               |   Release local latch for the process     |
|                     |                                           |
|     X               |   Release local latch for the process     |
|                     |   Downgrade X lock to S for the DBMS      |
|                     |                     (Optional)            |
+-----------------------------------------------------------------+

      In a single system different processes serialize by using a
latch which is memory-based.  In a multisystem environment where each
system has its own memory, typically, processes serialize by
replacing the latch by a global lock.  Global locking can have
significant message o...