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How Much Temporary Storage Am I Using?
Published: October 28, 2009
Hey, Joe:
My i5/OS partition disk storage is filling up and it hit 85 percent utilization today. How do I tell how much temporary storage space my system is using? If there's a lot of temporary storage, what can I do about it? I heard that if you IPL a partition, you can reduce disk usage.
--Mick
While an IPL can reclaim temporary storage space, it's wise to first check out how much temporary space is being used on the system, just to see if it's worth your while to IPL. Since iSeries, System i, and Power i machines generally run for months at a time, you probably want to ensure that you've done everything possible before you IPL the system. Here's a quick drill for examining temporary storage and for possibly doing something about it.
First, use this IBM-provided equation for calculating temporary storage utilization in a partition.
Temporary storage disk utilization =
(Current unprotected used storage / Total System ASP storage) / 10
You can retrieve the numbers for this equation from the Work with System Status (WRKSYSSTS) command display. The trick is to only focus on the numbers in the Auxiliary Storage area, which are found in the upper right-hand section of the WRKSYSSTS screen. Here's a sample of what that area might look like on a system where temporary storage is under control.
Work with System Status
Auxiliary storage:
System ASP . . . . . . : 3169 G
% system ASP used . . : 67.8219
Total . . . . . . . . : 3169 G
Current unprotect used : 21531 M
Maximum unprotect . . : 63069 M
On this system, the System ASP contains 3169 G of storage (about 3 Terabytes), which will be used for the Total System ASP Storage Number in your equation. It's important to note that even though we are talking about temporary storage for system jobs, temporary storage is still written to system Auxiliary Storage Pool (ASP) disk so we use the System ASP value in the calculation. The Current Unprotected Used number (21531 M) can also be plugged directly into the equation from this screen.
Using these numbers, here's what the equation to calculate the Temporary Disk Storage Utilization value for this system looks like.
Temporary storage disk utilization percentage =
(21531 / 3169) / 10 = .679 percent of disk
Since the Current Unprotected Used Storage number is listed in Megabytes and the Total System ASP Storage number is listed in Gigabytes, it's necessary to divide the resulting percentage by 10 to get the actual percentage used. For this example, temporary storage utilization is under 1 percent so there isn't an issue with reclaiming storage. But let's look at another example where temporary storage may be a real problem. We'll start with these WRKSYSSTS statistics.
Work with System Status
Auxiliary storage:
System ASP . . . . . . : 705.6 G
% system ASP used . . : 85.5388
Total . . . . . . . . : 705.6 G
Current unprotect used : 90000 M
Maximum unprotect . . : 110771 M
Which gives us the following equation for temporary storage disk utilization.
Temporary storage disk utilization percentage =
(90000 / 705.6) / 10 = 12.75 percent of disk
IBM states that it's normal for temporary storage to consume 5 percent or less of total disk storage, so if your temporary storage utilization is under that number, don't worry. However, if your system was gobbling up 12.75 percent usage of disk space like this one, you might want to do something about the situation. To determine which jobs are consuming temporary disk space, run the following Work with System Activity (WRKSYSACT) command to list your partition's active jobs by the amount of net storage being used.
WRKSYSACT SEQ(*STGNET)
This displays your partition's active jobs according to how much net storage (allocated storage less deallocated storage) each job is currently using. From the initial Work with System Activity screen, press the F11 key (switch view) three times to get to the storage view screen, which looks like this.
Work with System Activity SYSTEM
10/20/09 21:34:03
Automatic refresh in seconds . . . . . . . . . . . . . . . . . . . 5
Elapsed time . . . . . . : 00:00:02 Average CPU util . . . . : 15.4
Number of CPUs . . . . . . : 3 Maximum CPU util . . . . . : 19.7
Overall DB CPU util . . . : 3.7 Minimum CPU util . . . . . : 9.4
Current processing capacity: 2.50
Authorization Type . :
Type options, press Enter.
1=Monitor job 5=Work with job 6=Wait detail
Job or --------Storage-------- Total
Opt Task User Number Thread Allocated Deallocated Wait
RBREPORT1 QSYSOPR 014677 0000001F 34816 0 999.9
QDFTJOBD JOEH 014763 00000017 8696 705 28.0
DAILYEOD BUBBAB 014663 00000040 2577 971 .0
WEBSITE1 QTMHHTTP 998479 00000005 13385 13027 .0
WEBSITE2 QTMHHTTP 998463 00000004 50874 50618 999.9
PORT50410 MIMIXOWN 984503 00000002 260 65 .0
Although it's not obvious, this screen displays all the active system jobs by net allocated storage. The screen doesn't show net allocated storage for each job, but you can easily calculate it by subtracting the Storage→Deallocated number from the Storage→Allocated number for each job. Understand however that WRKSYSACT only shows data for jobs that have had activity since the last data collection. There may be other system jobs taking up temporary storage that weren't active when you ran WRKSYSACT. Those jobs won't show up in the display until they show some activity.
If you notice any jobs that are taking up too much net storage, end and restart those jobs to see if that affects your temporary and total disk storage utilization numbers. If that doesn't help, you can take other measures, including IPLing the system. To help troubleshoot problems with allocating excessive temporary storage on your system, IBM offers a few other ideas in Technical Software Document 22152301, Temporary Space Growth Problem Debug.
HTH
--Joe
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