Author Archives: Martin Packer

(Originally posted 2006-03-30.) Long ago the DB2 REORG utility traded memory for speed with SORTKEYS and SORTDATA. The latter caused the object being REORGed to be unloaded and externally sorted (eg using DFSORT). (SORTKEYS was similar but for the keys to REORG the indexes.) This is fine if you have the memory to drive eitherContinue reading “More REORG Utility Flexibility”

(Originally posted 2006-03-30.) Just briefly, here are some Access Path fixes I’ve been meaning to talk about: PK14923 QUERY COST ESTIMATE IS TOO HIGH IN SOME CASES PK16521 ONE FETCH INDEX ACCESS (I1) NOT USED WITH DUPLICATE PREDICATES PK15143 POOR QUERY PERFORMANCE WHEN SORT MERGE JOIN IS CHOSEN AND MULTIPLE JOIN COLUMNS ARE POSSIBLE ORContinue reading “Some SQL Access Path Improvements”

(Originally posted 2006-03-30.) One of the themes for Distributed access to DB2 that I talk about is Network Flows Optimisation, in particular ensuring that DB2 is taking advantage of such things as blocking… When DB2 sends rows back to a DDF caller it can block them or return them singly (and indeed the degree ofContinue reading “DDF Row Counts Bug”

(Originally posted 2006-03-30.) I present at conferences on what I call New World DB2 application performance, by which I mean such things as Stored Procedures, SAP R/3 and BW, Distributed (DDF) and JDBC. I do this because I think us mainframe performance people need to lead conversations on DB2 application performance that actually acknowledge whatContinue reading “DB2 As A Web Services Provider”

(Originally posted 2006-03-10.) A little off-topic, perhaps, but I’ve just installed the second Alpha of Lotus Sametime 7.5, IBM’s recently-previewed new instant messaging client. I would’ve liked to have installed the first Alpha but I’ve been working hard on behalf of one of my favourite clients until yesterday. There’s that phrase again, Brian. 🙂 Actually,Continue reading “Lotus Sametime 7.5 Alpha 2”

(Originally posted 2006-02-24.) My friend Frank Kyne in the ITSC Poughkeepsie center sent me a link to this draft RedPaper. It provides useful information, from some realistic benchmarks, on a number of Coupling Facility configuration options. I haven’t exactly been idle in this space recently: One of my favourite clients has sent me their DB2Continue reading “Useful RedPaper: Coupling Facility Performance: A Real World Perspective”

(Originally posted 2006-02-24.) APAR PK18018 documents a condition where the use of either the FETCH FIRST n ROWS or OPTIMISE FOR n ROWS clauses leads to a suboptimal access path. Occasionally you can get an ABEND. This APAR is marked for DB2 Version 8 only.

(Originally posted 2006-02-22.) APAR OA15323 documents the F CATALOG,REPORT,CATSTATS and F CATALOG,RESET,CATSTATS commands which became available with z/OS Release 7. The REPORT command will list I/O access statistics, as well as BUFNI, BUFND, and STRNO information for each catalog. To limit the command to just a single catalog there is a second format (using theContinue reading “Undocumented Catalog Address Space Command – CATSTATS”

(Originally posted 2006-02-22.) APAR OA14572 documents a problem where there is excessive SRB time and an increase in EXCPs for the index component of a VSAM KSDS accessed by RLS when two or more RPLs are adding records to the end of the data set.

(Originally posted 2006-02-22.) APAR PK15454 documents an extension to DB2’s EXPLAIN function which makes correlation of the various tables involved much easier. This enhancement is used by Visual Explain but can also be used by people querying the tables EXPLAIN produces, in particular DSN_FILTER_TABLE and DSN_PREDICAT_TABLE.</p. When you EXPLAIN a statement it produces rows inContinue reading “Enhancement For Users of DB2 EXPLAIN”