Achieve faster IFS save times using SAV with ASYNCBRING

Abstract

An enhancement has been made available in IBM i 6.1 and later releases, which may help with integrated file system SAV performance.

Content

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ASYNCBRING will enable objects to be asynchronously brought into memory early so they will not need to be paged in when first accessed by the SAV processing. While results will vary, testing in the lab and by a few customers have shown some dramatic improvements - up to 60% faster save times in some cases. The performance gain seen is dependent on the directory structure, number and size of objects saved, amount of memory available, and the system configuration. This enhancement is available on both the SAV command and QsrSave() API.

From the PTF cover letter:
A new parameter will be added to the SAV command and a new key added to the QsrSave API which will specify whether objects should be asynchronously brought into memory during the save processing.

Asynchronous brings will only be done when saving objects from the root ('/'), QOpenSys, and user-defined file systems.

SAV command help text for ASYNCBRING:
Asynchronous bring. Specify whether objects should be asynchronously brought into memory during the save processing.

Depending on the directory tree structure, the amount of memory available, and the number of objects which qualify for the save, asynchronously bringing the objects may improve save performance. The best performance improvement may be seen with a well balanced directory tree in which all objects qualify for the save. In situations where a large number of objects reside in a single directory, few objects qualify for the save, or the system is memory constrained, performance may degrade with ASYNCBRING(*YES) specified. The default is *NO.

The possible ASYNCBRING parameter values are:

• *NO - Asynchronous bring is not done
• *YES - Asynchronous brings are done

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