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May 2006, Week 3

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Subject:
more info B-Tree Extent system table
From:
Craig Lalley <[log in to unmask]>
Reply To:
Craig Lalley <[log in to unmask]>
Date:
Tue, 16 May 2006 08:02:35 -0700
Content-Type:
text/plain
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text/plain (64 lines) 
Some more information....
  
  This is an Ecometry site.
  
  When 100-200 agents are logged on, the B-Tree extent table is around  27%.   When 1600 agents are logged on, the B-Tree extent  table goes above 85%.
  
  The agents have basically the same files open.
  
  -Craig


-----Original Message-----
From: HP-3000 Systems Discussion [mailto:[log in to unmask]] On Behalf Of Craig Lalley
Sent: Tuesday, May 16, 2006 7:25 AM
To: [log in to unmask]
Subject: [HP3000-L] B-Tree Extent system table

This is a 7.5 system, fully patched with 325 LUN's (disk drives).

The system crashed when it ran out of B-Tree Extents.

I have included some documentation I have found.   There are two Extent B-Tree system tables.

54 Extent B-Tree
56 Extent B-Tree AR

I am concerned about the first one.

In the documentation they appear to be the same thing.

I made a false assuption that it had do with number of file extents, that does not appear to be the case.

Can someone explain to me what B-Tree Extents are and how I can minimize them?
 
Regards,

-Craig


FILE EXTENTS 
  This resource is also referred to as the Extent B-Tree Table. Disk  files and virtual memory disk areas are allocated in contiguous pieces  called "extents". Each node in the Extent B-Tree can describe up to  four extents. If an object contains more than four extents, it will use  additional notes as needed. Every non-resident object with fixed access  rights will 
 require one or more nodes in this table when it is mapped in (opened). 
  NOTE: Objects with fixed access rights are those for which all pages  have identical read and/or write access as well as the same privilege  level. Extent information about objects with variable access rights is  kept in the Extent AR B-Tree Table. 
 
 ACCESS RIGHTS 
 This  resource is also referred to as the Extent B-Tree AR Table. Disk files  and virtual memory disk areas are allocated in contiguous pieces called  "extents". Each node in the Extent AR B-Tree can describe up to eight  extents. If an object contains more than eight extents, it will use  additional nodes as needed. Every non-resident object with variable  access rights will obtain one or more nodes in this table when it is  mapped in (opened). NOTE: Objects with variable access rights are those  for which not all pages have identical read and/or write access or the  same privilege level. NM program files and NM library files are  examples of objects with variable access rights. Page 0 has write  access in addition to the read/execute access that is given to the  other pages of the file. Extent information about objects with fixed  access rights is kept in the Extent B-TreeTable. 



  
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