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2021541 - Server runs slow due to table scans with regular page allocation - SAP ASE

Symptom

  • The sp_sysmon output shows 90% CPU usage in Adaptive Server Enterprise (ASE) engines.
  • The top command shows a huge increase in the RES memory usage.
  • From the boot sequence, the ASE server is trying to ask more memory than Linux operating system limit can offer.
  • Huge Page memory can't be used.
  • The following error in the boot sequence in the ASE error log:

server  Configuration file '/opt/sybase/xxx.ASE.cfg' has been written and the previous version has been renamed to '/opt/sybase/xxx.ASE.001'.
server  The configuration option 'max memory' has been changed by 'sa' from '5000000' to '6043456'.
kernel  Allocating a shared memory segment of size 1908015104 bytes.
kernel  Could not allocate memory using Huge Pages. Allocated using regular pages. For better performance, reboot the server after configuring enough Huge Pages.
kernel  Attempt to attach shared memory (id 1822851079) at address 0x2aad1c000000, with flags 0 failed
kernel  Cannot attach shared memory : error = 5 (Input/output error)
kernel  os_create_region: shmat(1822851079): Input/output error
kernel  kbcreate: couldn't create server region 0.

  • When there are queries using lots of table scans, there is a huge increase in the top memory and 90% CPU busy in ASE engines from sp_sysmon output.

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Environment

  • SAP Adaptive Server Enterprise (ASE) 15.7 
  • SAP Adaptive Server Enterprise (ASE) 16.0

Product

SAP Adaptive Server Enterprise 15.7 ; SAP Adaptive Server Enterprise 16.0

Keywords

Huge Pages, Regular Pages, performance problems , KBA , BC-SYB-ASE , Sybase ASE Database Platform (non Business Suite) , Problem

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