RE: Model 270 At V5R2 Is Dead Toad Slow Running JDE One World....... -- MIDRANGE-L

Mike, I don't know if this happened from the upgrade to V5R2 - the issue here presented is from all the way back to V4R1. But it might help to look at the ACCPTHSIZ attribute of your keyed files. From a Redbook: ==================================================== 16.14 Considerations for 1TB Maximum Access Path Size

On V4R1 systems and later, the default value for access path size for the Create Physical File and Create Logical File commands (CRTPF and CRTLF) is 1 terabyte (TB). On prior systems the default is 4GB. This means that instead of a three-byte index, a four-byte index is built with the implicit ability of granularity on the index.

The four-byte index circumvents a lot of seize conflicts. However, this change may have an impact on the implicit access path sharing for database files created prior to V4R1.

If you have an existing database with all three-byte indexes and you create or recreate a file with an index, that index becomes a four-byte index by default. It does not have the ability to implicitly share an existing access path of a three-byte index.

From a functional point of view, you cannot see any difference since the application runs in the same way. However, it can impact overall system performance when more implicit shares are removed and eventually a large number of access paths exist for both the three and four-byte versions.

Recommendation

Do not mix three- and four-byte access paths.

There are three approaches to avoid mixing three and four-byte access paths:

1. Leave the Access Path Size parameter (ACCPTHSIZ) default to *MAX1TB and recreate the database so all access paths are in four-byte mode. The downfall of this approach is that recreating the database can be time consuming.

2. Change the ACCPTHSIZ default back to *MAX4GB. This does not avoid potential seize conflicts, however.

3. Use DSPFD and DSPDBR commands for the critical files (those with large access paths and/or heavily used) to keep the files in synch with access paths. Migrate to four-byte indexes in a phased manner.

Use the CHGPF command to change the access path size of a physical file and the CHGLF command to change the access path size of a logical file ====================================================

The locking is reduce because, as I understand it, locking is more granular in the 4-byte version - fewer contiguous records are tied up.

Fixing shared access paths can be done by saving the physical and all dependent logicals with a single save command, including access paths, then restoring them with a single restore command. If the system will determine that an access path can be shared, then it will create a new shared path, instead of restoring the multiple access paths that were saved.

HTH

Vern

At 10:22 AM 4/12/2003 -0700, you wrote:

Mark,

I did that when I went to V5R1 over all the JDE libraries.  As I recall,
it was just a V5R1 thing coming over from V4R5.  I am going to do some
more poking around and see what I can come up with here.

I have a full system backup scheduled to run at 01:00 AM tomorrow
morning along with an IPL.  If it is still DEAD TOAD slow, I will in
fact run object conversion over the libs.

Thanks!

Mike Shaw