I was at a customer site the other day, working on a server I hadn’t worked on before doing routine maintenance. HMC upgrade, firmware & ptf install. So what? I hear you ask. Well, everything was going well until I started the save21 (Entire System Save) prior to the ptf install.
It took that long to get going, I really thought I had broken something but I waited longer and after 40 minutes up popped a screen which said “saving library 2 of 1310. This worried me a lot, a quick calculation came up with a save21 time of 37 hours! Thankfully things speeded up from there and 4 ½ hours later I had a save21 tape.
During my unexpected 4 ½ wait I wondered if it was possible to predict how long the save21 was going to take. Well to my surprise there is a way of estimating save21 run time. In library QUSRSYS there is a 2000 byte data area called QSRSAV21 which contains information about previous save21’s.
Type DSPDTAARA QUSRSYS/QSRSAV21 to view the data area which looks like this.
There is a full 2000 bytes display of the data area at the end of the article if you want to see more.
Once it fills up it after 5 or so save 21’s it goes back to the beginning and starts to overwrite. Notice with this example the last line of the latest save21 begins in offset 0
Taking my save21 as the example you can determine the following about the save21 run on 12/12/2019. The information starts in offset 1150
20191212130154 ENDSBS ß System was put into restricted state at 13:01:54
20191212130243 SAVSYS ß SAVSYS started at 13:02:43 and took about 18 minutes to complete
20191212132007 SAVLIB ß SAVLIB started at 13:20:07 and took about 3 hours 41 minutes to complete
20191212170111 SAVDLO ß SAVDLO started at 17:01:11 and took about 30 seconds to complete
20191212170141 SAV ß SAV started at 17:01:41 and took about 37 minutes to complete
20191212173840 SAVIASPS ß SAVIASPS started at 17:38:40 and took less than 1 second to complete
20191212173841 STRSBS ß STRSBS started at 17:38:41
20191212203442 ******** ß Go SAVE21 job completed at 17:38:41 on 12/12/2019 and took 4 hours 37 minutes to complete
The data in bold is the date in yyyymmdd format. The 6 digits after the date is the time the save command started in hhmmss format.
The information in the data area contains the starting date and time of each major step in the save operation and the device used. The ending date and time of the operation is identified with asterisks.
So, if you are ever asked, how long would it take to backup the entire system, now you have a way of finding out how long it took the last time a save21 was run. This will give you a good basis for estimating how long it’s going to take.
ProTip: If you are running IBM i 7.2 or newer, remember you can save time on your backup by reducing the TCP Timer to *NONE. The default is 300 seconds, and this is used twice, so you can get 10 minutes back from your backup there and then.
The Entire 2000 bytes