System-managed access-path protection

 

System-managed access-path protection (SMAPP) allows you to use some of the advantages of journaling without explicitly setting up journaling. Use SMAPP to decrease the time it takes to restart your system after an abnormal end.

SMAPP is a way to reduce the time for an iSeries™ server or independent disk pool to restart after an abnormal end. An access path describes the order in which records in a database file are processed. A file can have multiple access paths, if different programs need to see the records in different sequences.

When the system or an independent disk pool ends abnormally, the system must rebuild the access paths the next time you restart the system, or vary on an independent disk pool. When the system must rebuild access paths, the next restart or vary on operation takes longer to complete than if the system ended normally.

When you use SMAPP, the system protects the access paths so the system does not need to rebuild the access paths after an abnormal end. This topic introduces SMAPP, describes SMAPP concepts, and provides setup and management tasks.

• Benefits of SMAPP
  System-managed access-path protection (SMAPP) can greatly reduce the amount of time it takes to restart your system or vary on an independent disk pool, after an abnormal end.

• How SMAPP works
  The purpose of system-managed access-path protection (SMAPP) is to reduce the amount of time it takes to restart the system or vary on an independent disk pool, after an abnormal end.

• How the system chooses access paths to protect
  The system periodically examines access path exposure and estimates how long it would take to rebuild all the exposed access paths. If the rebuild time exceeds your target recovery times for access paths, the system selects additional access paths for protection.

• Effects of SMAPP on performance and storage
  System-managed access-path protection (SMAPP) is designed to have minimal effect to your system. Though it is minimal, SMAPP does affect your system's processor performance and auxiliary storage.

• How SMAPP handles changes in disk pool configuration
  When you restart the system, the system checks to see if your disk pool configuration has changed. The system may change either the size of the SMAPP receiver or the placement of the receiver based on the change to the disk units.

• SMAPP and access path journaling
  In addition to using system-managed access path protection (SMAPP), you can choose to journal some access paths yourself by using the Start Journaling Access Path (STRJRNAP) command. This is called explicit journaling.

• SMAPP and independent disk pools
  Use SMAPP to limit recovery time for access paths that reside within independent disk pools.

• Starting SMAPP or changing SMAPP values
  Use the Edit Recovery Access Path (EDTRCYAP) display to start or change values for system-managed access-path protection (SMAPP).

• Displaying SMAPP status
  You can display many types of status for SMAPP.

 

Parent topic:

Journal management

Related concepts
Reasons to journal access paths Reasons to journal before-images Functions that increase the journal receiver size