OK, so I downloaded the cover letter for MF26466
DESCRIPTION OF PROBLEM FIXED FOR APAR MA22147 :
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Some applications such as SQL create several objects in QTEMP
and then later remove them. On some server systems with a
small number of disk arms, this causes a slow down of system
performance due to the number of disk writes used to
insure that the libraries are forced to disk.
QTEMP libraries are deleted on the next IPL. As such it is
not absolutely necessary to force these libraries to disk at
run time.
CORRECTION FOR APAR MA22147 :
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This PTF reduces the number of disk writes done to QTEMP
libraries.
Some performance is gained during normal operation of OS/400
for some applications. The customer is trading run-time
performance improvement for a degradation in some abnormal
IPL situations. The system may take MUCH longer to IPL
after some abnormal system terminations.
CIRCUMVENTION FOR APAR MA22147 :
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Run the system at security level 50.
DEFAULT INSTRUCTIONS :
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THIS IS A DELAYED PTF TO BE APPLIED AT IPL TIME.