Top Secret SECCACHE And CACHE Control Options

Products

• Top Secret

Issue/Introduction

What is the difference between the SECCACHE and CACHE control option?
Is there a way to determine the initial size for the SECCACHE control option?

Resolution

SECCACHE provides a cache for Top Secret to place security records that reflect the status of a user following a RACROUTE VERIFY request. This increases system performance by: 

• Reducing CPU cycles in both the user and security address spaces required to complete subsequent RACROUTE VERIFY requests.
• Reducing I/O against the security file when the file is shared between multiple systems. 

The CACHE control option provides an area of memory for Top Secret to place frequently used items from the security file. Provision for sufficient CACHE reduces I/O against the security file and increases system performance. 

The CACHE provides benefits in two areas:

• The first is that users commonly sign on multiple times in a short duration of time. In some cases this is because of the log on mechanism as in TSO, or logging on to multiple regions such as CICS.
• Secondly, the CACHE benefits profile sharing by allowing I/O performed on behalf of one user to benefit another user logging onto a different address space.

There is no science to picking the initial size for SECCACHE. Some shops may have more signons happening in a day, but have less acids. The 2 operands that are the key to determining, if you need to make the size bigger or the Index bigger are:

• NOSPACE
• NOINDEX.
• The Index default is 5000.           Below is the information on NOSPACE and NOINDEX. If these numbers are large, than the Index or Size needs to be increased (or both).
  
  NOSPACE                                                                  
  Number of data area allocation requests failing due to no available space. A large number indicates the data size allocated to the cache     
  is too small. You can attempt to recover space with a CLEAR,EXP=nnn request. 
  
  NOINDEX                                                                  
  Number of index entry allocation requests failing due to no available space. A large number here indicates the number of index entries         
  allocated to the cache is too small. You can attempt to recover space with a CLEAR,EXP=nnn request.                                            
  
  The SECCACHE size value can be increased by issuing the following commands:                                                                
  
  F TSS,SECCACHE(OFF)                                                       F TSS,SECCACHE(SIZE=xxxx,INDEX=xxxxx,EXP=x,WARN=xx)                       
  
  For example, to increase the size of the SECCACHE to 2 gig, you would issue the following commands... You would include the desired settings for INDEX, EXP and WARN in the command (even if they are not being changed).         
  
  F TSS,SECCACHE(OFF)                                                       
  F TSS,SECCACHE(SIZE=2048,INDEX=30000,EXP=6,WARN=80)                       
  
  The F TSS commands are issued from the console. If you prefer to issue the commands from, say, option 6 in TSO, use TSS MODIFY instead of F TSS,.