DB2 - Tips and Tidbits for the DB2 for z/OS Systems Programmer

/ 20 January 2009 / EDS LIMITED DISTRIBUTION

DB2 – Tips and Tidbits for the DB2 for z/OS Systems ProgrammerRebecca Keller US Software Services

20 January 2009 / EDS LIMITED DISTRIBUTIONTips and Tidbits for the DB2 for z/OS Systems Programmer 2

Tips and Tidbits for DB2 z/OS

• Installation•Maintenance•System Administration•Problem Determination and Resolution•Local and Disaster Recovery•Performance and Tuning•Support DBA & Application Development Staff•Miscellaneous Tidbits

What is a Systems Programmers Job Functions?


Installation



•Create naming conventions before you start•Use Names that indicate Test vs. Production •SSIDIRLM for IRLM Proc Name•Use *Meaningful* WLM APPLENV names•Use System Scope IEFSSN entries unless planning for Data

Sharing - Install on all LPARS•Do not put DSNLOAD in the LINKLIST•Use CRC that includes the SSID, not just a single character•Use aliases for software

Installation



•Use symbolic aliases for Data Sharing •Use SMS management for datasets•Check PDS/e and GSO options for LINKLIST datasets•Plan for Data Sharing carefully. You cannot permanently

remove a member from a group, only QUIESCE the member

•Create an HFS file system for each subsystem•Mount HFS file systems without the version identifier in

it: /usr/lpp/db2/ssid•Auto-mount HFS file systems

Installation



•Use SCHENV for job execution •Do not use SMP/e libraries for execution libraries•Use granular DB2 authorities – Do not hand out SYSADM •Set the Correct CCSID at installation time•Create at least one Work File Table space (V8) with

secondary space

Installation


Maintenance



• IBM recommends maintenance quarterly. Is that realistic? •At least receive/apply the maintenance in SMP/e regularly

(monthly)•Read Cover letters – check for INCORROUT and Corruption

and see if the scenario applies•Apply ERLY code more frequently, then you are at least

prepared for any upcoming maintenance•Read the hold data – can have interesting information and

alerts you of the actions required•Some interesting tidbits of recent maintenance:

– End of LOG RBA– Diagnosis Guide sent in electronic form – AO types which are generally changes in message output that can cause automation to break– Hidden explain tables

Maintenance


System Administration


0


•Active Logs – size them to fit on a single tape, if using real tape - still a good recommendation

•Dual active and archive logging•Specify the same active log sizes for all LOGCOPIES•Spread them on different DASD devices and controllers or

use PAV/striping•Use DASD TMM/HSM solution if very high volume logging•Archive log cancel offload command – first thing to try, but

it does not always work



1


•ARCHIVE LOG SCOPE(GROUP) for Data Sharing•Errors offloading archive logs or BSDS?

Duplicate the other copy•Things to Automate:

– Restart DB2, only three times so no recursive restarts– Restart Light for Data Sharing for a failed LPAR– DSNJ110E (Last Log) messages. Not held highlighted by

default



2


•Things to Monitor:– DSNI013I – SSID DSNIDIFS Potentially Inconsistent– SYSCOPY for successful completion of image copies– SYSCOPY for no LOAD/REORG LOG YES– BSDS for LOG status, make sure there are none with

permanent errors– Growth on user managed table spaces, approaching the

2GB limit– Space on private volumes, so that extents can be taken – INDOUBT threads, may need to reset when coordinator is

cold started (e.g. DataPropagator Tasks)– Growth in secondary space on DSNDB07



3


•DSNZPARM Settings:– CHKFREQ: 2-3, but log size matters– URLGWTH: Use to catch threads that commit

infrequently– URCHKTH: No more than 24 hours, for URID that may

become in-doubt– TCPKEEPALIVE: To match your client thread clean up routines– IDTHTOIN: Match to your TCPKEEPALIVE– OPTHINTS: ON, just in case you need to use hints in V8– TSTAMP: Definitely timestamp logs, can get a much

quicker idea of rate of logging over time– CATALOG: YES for archive logs



4


•DSNZPARM Settings:– ACCUMACC: NO gets better reporting for DDF

threads– LOGAPSTG: 100MB, or else only good on DB2

restart– MAX_NUM_CUR: 99999– MAX_ST_PROC: 99999– SQLINTRP: Disable to Avoid -950 SQLCODES– UNION_COLNAME_7: YES, restores V7 behavior

•Use Set SYSPARM, table in Install guide for the items that can be set dynamically

•Watch for DSNZPARM additions via APAR, like OPTIX* performance “enhancements”



Problem Determination and Resolution


6


•Have a tool kit ready•Standard jobs: TERSE, FTP, DSN1LOGP, DSN1COPY,

DSN1PRNT, DSNJU004, EREP •Less used utilities: DSN1SDMP, DB2PLI8, DIAGNOSE•Verify your dump dataset MAXSPACE, 2GB is a good start •Verify your dumps are copied off SYS1.DUMPxx datasets•Verify IEADMC* and IEADMP* members are set up with the

correct parameters to get the storage areas IBM will want to see



7


•Check the SYSLOG, sometimes pertinent messages are there and not in the JESLOG of the DB2 address space

•Beware that COMMDUMPS will slow down a system as the dump is being taken, can cause MVS paging from DUMPSRV

•Get a dump report created regularly from all SVC dumps. Sometimes issues are occurring and no one is reporting/noticing them

•Use IPCS, sometimes helpful to do the front end debugging•Use GTF for traces instead of SMF to avoid having to send

a lot more data than necessary• IBMLink and search strings:http://www-01.ibm.com/support/docview.wss?rs=64&uid=swg21210011



8


•Know how to disable dump analysis tools •Try the “native” IBM way, if using a 3rd party tool,

(especially utilities) to eliminate that potential point of failure

•Verify that SMF and LOGREC are split off daily



9


•Handy MVS and DB2 commands:– D O Operator Information– D U,,,NNNN,1 Device Status– D R,L Outstanding Replies– D A,L Show active Tasks– D PROG,APF APF (and LNKLST) entries– D WLM,APPLENV=* WLM Environment Status– DUMP Force a dump to be taken– SETPROG Update APF and LNKLST – SETSSI Add a Subsystem– SLIP SET SLIP Traps– F IRLMPROC, Many options Modify or “Talk” to the IRLM– D XCF,….. Cross System Coupling Facility – CANCEL THREAD NOBACKOUT DB2 cancel thread command – DIS DB(*) SP(*) RESTRICT DB2 display of restricted objects



Local and Disaster Recovery


1


•You can initialize SYSUTILX, but might need to start force•Use LISTDEF for backups and recoveries•Beware DB2 managed user indexes on catalog and

directory•BSDS will auto-recover on V8•BSDS is reformatted for V9 in print log map, the DDF

section is above the active log report•Recover postponed cancel in V9



2


•Catalog datasets for image copies•Must be “Install SYSADM” to recover SYSUSERAUTH•DSNR031I -DB03 DSNRTIMR PROCESSING LOG RECORD AT

RBA will show status of log processing while restarting DB2•Practice, Practice, Practice, Try things on your sandbox



Performance and Tuning


4


•Request performance baseline before version upgrades

•Look for what has changed (Trust but Verify)•Beware of skewed distribution statistics for

non-unique indexes•Use RLIMIT and predictive governing•Use UNLOAD utility instead of DSNTIAUL when

practical – but benchmark the difference•Use CACHEDYN and MAXKEEPD for dynamic

SQL

Performance and Tuning


Support DBA and Application Staff


6


•Recommendations for DBA and Developers: – Use “Online” utilities (SHRLEVEL Change)– Use LISTDEF and Templates– Use log NO for utilities and Inline Copies– Select Count(*) before deleting/updating rows in SPUFI or DSNTEP2, if

more than 1000, write a program– Beware “over-indexing”, particularly with non-unique indexes– Beware of using new features immediately– Set VPSEQT=0 if you want to disable sequential pre-fetch– Run better RUNSTATS, and perhaps not as often– Use real time statistics and the interface with DFSORT for utilities– Bind with explain and use an index on the PLAN_TABLE– Use the new enhanced explain output features (DSNTESC job)– Use packages and versioning in V8, free old versions

Support DBA and Application Development Staff


Miscellaneous Tidbits


8


•DSNZ016I -D2T8 DSNZINIT in V9, shows from where exit modules were loaded

•SQLDA is larger in V8 than hex ‘FF’, can cause assembly errors•New DISPLAY DB(*) restricted status in V8 and V9 •Sliding scale and z/OS extent consolidation•DSNY014I DB2 started in maintenance mode – must have

“Install SYSADM or SYSOPR” authority to access•Pre-compiler issues with some characters on z/OS, use

CCSID(1047) on the pre-compile to work around the problem



9


• -805 SQLCODE thrown from SPUFI in V8 CM with Get diagnostics•You can now reassign “Install SYSADM” with Set SYSPARM•“Local” Date and Time Exits, you need for ASCII and Unicode

versions in NFM•&SPRMCTU SETC ‘1‘ in DSN6SPRC, to be able to update the

catalog using SPUFI•Watch your DDCONS and DETAIL settings in SMFPRM* members



0


• ICOPY status on DSNDB01 objectsDSNT360I -D2T8 *********************************** DSNT361I -D2T8 * DISPLAY DATABASE SUMMARY * GLOBAL DSNT360I -D2T8 *********************************** DSNT362I -D2T8 DATABASE = DSNDB01 STATUS = RW DBD LENGTH = 14200 DSNT397I -D2T8 NAME TYPE PART STATUS PHYERRLO PHYERRHI CATALOG PIECE -------- ---- ----- ----------------- -------- -------- -------- ----- DBD01 TS RW SPT01 TS RW SCT02 TS RW SYSUTILX TS RW SYSLGRNX TS RW DSNSCT02 IX RW DSNSPT01 IX RW,ICOPY DSNSPT02 IX RW,ICOPY DSNLUX01 IX RW,ICOPY DSNLUX02 IX RW,ICOPY DSNLLX01 IX RW,ICOPY DSNLLX02 IX RW,ICOPY ******* DISPLAY OF DATABASE DSNDB01 ENDED ********************** DSN9022I -D2T8 DSNTDDIS 'DISPLAY DATABASE' NORMAL COMPLETION



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DB2 - Tips and Tidbits for the DB2 for z/OS Systems Programmer