Controlling Access Path Rebuilds in iCluster to Speed-Up the Apply
In iCluster 7.1 we introduced a new feature called the Access Path Rebuild Controller. Yes I admit it wasn’t the sexiest name for a new feature but PowerHA was already taken! What the APRC does is allow you to determine when the operating system will be rebuild the access paths for a specific set of files by changing the file’s Access Path Maintenance parameter from *IMMED to *DELAYED automatically and then changing it back again through a cycling process. This is important because with large physical files with a large number of logical files attached, the apply process could be delayed as the OS rebuilds those access paths.
The Access Path Rebuild Controller is reached via Menu Option 51 Maintain Access Paths on the second page of the iCluster Main Menu.
The first thing you need to do is create an Access Path List that will contain a list of all the physical and logical files whose access path maintenance parameters you want to change to *DELAYED or to manage. The default name is DMACCPLST in library ICLUSTER. Use F6 to bring up the command to create an access path list or from a command line you can use the DMCRTAPLST command. This is shown in the screen below.
Next you can either use Option 2 next to the access path list you just created as shown below to add a single access path:
or use the DMADDPFAPL to add a physical file and all its associated logical files to the access path list that you created. A good candidate for this is a large file with a large number of logicals built over it that has large numbers of inserts, updates or deletes. In this screen shot we are adding the customer file and all its logicals.
Then you use either Option 1 for Start maintenance on the Work with Access Path Lists screen, or the DMSTRAPM to actually start the process – pointing it to the access path list that was created and as in this case specify *CYCLE to change the access paths from *IMMED to *DELAYED every 60 seconds, and also do it in batch. You can also optionally tell iCluster to load this file into memory to make the rebuild even faster.
Take the APRC for a test drive next time you notice a large apply latency!
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