Unfortunately, systems periodically experience an unplanned outage. Use the availability tools described here to restart your system as quickly as possible after an unplanned outage.
Before your system powers down, it performs certain activities
to ensure that your data is protected and that jobs are ended in a controlled
manner. When you experience an unplanned outage, your system cannot perform
these activities. Each of these tools should be used together to quicken the
start up times for your system. 
For more details on what happens when your system ends abnormally, see Start and stop the system.
Use the Reducing iSeries IPL Time experience report to learn how to control the time that it takes to start your iSeries server.
System-managed access-path protection (SMAPP)
An access path is the route an application takes through a database file to get to the records it needs. A file can have multiple access paths, if different programs need to see the records in different sequences. When your server ends abnormally, such as during an unplanned outage, the system must rebuild the access paths the next time it starts, which can take a long time. When you use system-managed access-path protection, the system protects the access paths so they do not have to be rebuilt when your system starts after an unplanned outage. This will save you time when you restart your server, which will enable you to get back to your normal business processes as quickly as possible. For detailed information on SMAPP, see System-managed access-path protection.
Journaling access paths
Like SMAPP, journaling access paths can help you to ensure that critical files and access paths are available as soon as possible after you restart your server. However, when you use SMAPP, the system decides which access paths to protect. Therefore, if the server does not protect an access path that you consider critical, you may be delayed in getting your business running again. When you journal access paths, you decide which paths to journal.
For more details on journaling access paths, see SMAPP and access path journaling.
SMAPP and journaling access
paths can be used separately. However; if you use these tools together, you
can maximize their effectiveness for reducing startup time by ensuring that
all access paths that are critical to your business operations are protected.
Protecting your access paths is also important if you plan to use
any disk-based copy services, such as cross-site mirroring or IBM TotalStorage
Enterprise Storage Solution (ESS) peer-to-peer copy features, to avoid rebuilding
access paths when you failover to a backup server.
Independent disk pools
When a system is started or restarted, you can start each independent disk pools individually. By starting each independent disk pool separately, the system can be made available more quickly. You can prioritize the workload so that critical data becomes available first. You can then vary on independent disk pools in a specific order based on this priority. See Example: Make independent disk pool available at startup for more information.