Monitor before-image size

 

It is a good idea to monitor the growth of before-image (bi) file. It will give the early warning that something goes wrong if bi file suddenly starts growing out of usual size. I set a rather hefty fixed length size bi plus a variable size extent. Then I set -bithold to little less than of fixed length of my bi file(s). That way in case of crash I have enough room for recovery. Say, my total allocated bi size is 20GB then I set -bithold to about 9.7GB. My normal bi usage is not more than 2GB. I use proutil bigrow to grow it to that size and use the following program to send me alert if before-image high watermark is more than 25% of total allocated space, in my case 5GB. That way I have time to make a decision before bi reaches -bithold.

 

find _AreaStatus where _AreaStatus-Areanum = 3 no-lock no-error.

if _AreaStatus-Hiwater / _AreaStatus-Totblocks * 100 > 25 /* % */ then

/* code to send alert message */

 

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