IDMS

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IDMS REXX in BT

• Iain Robertson
• IDMS DBA
• British Telecom
• iain.dk.robertson_at_bt.com

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IDMS REXX in BT

• Subject
• BT uses REXX to automate various DBA functions
  for its CSS database.
• This will look at some techniques used, and some
  of the ways BT uses REXX to make the DBAs life
  easier.

3
CSS some background

• CSS Customer Service System
• BTs main Customer Facing computer system
• Order Handling
• Fault Reporting
• Billing

4
CSS some background

• 29 MVS images
• 3 CVs per image
• 1 update, 2 Read only
• 0.5Tb 0.7Tb per database. 13.5Tb total
• 1,500,000 2,500,000 tasks/day
• 80,000 lines of REXX code

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CSS some background

• Originally, each database had its own DBA team.
• Now managed by 2 DBAs, plus 3 Central Support
  Team members
• Therefore, more procedures need to be automated,
  to free DBAs for more important work

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REXX and CSS

• REXX applications fall into 3 categories
• Automating trivial maintenance functions
• Automating mundane DBA functions
• Automating emergency functions

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REXX brief introduction

• Replacement for CLISTS
• Can be executed in TSO, or via batch job

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REXX brief introduction

• Stem variables
• EXECIO command
• String parsing
• Linking to programs, with optional parameters

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Trivial functions

• EXAMPLE
• Analysing output from utility programs
• Either user written programs, or CA-supplied
  utilities (IDMSBCF, UCFBATCH)

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Trivial functions

• Journal Recovery Flag problem
• WTOEXIT to write date/time of journal swap
• When problem occurs, job submitted
  automatically.

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Trivial functions

• Job consists of
• Step to run UCFBATCH to run user written
  checker program in CV
• Step to run REXX exec to determine
• Steps to reset journal recovery flag
  (user-written program)

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Trivial functions

• REXX exec
• Reads SYSLST file produced by UCFBATCH step
• Looks for messages beginning RF issued by the
  checker program
• Return code based on what it finds
• 0 Flag has reset itself
• 1-4 Safe to reset flag on JxJRNL
• 8 Unable to reset flag

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Trivial functions

• Sample SYSLST input to REXX
• SIGNON UCC7IDM
• IDMS DC258002 V10 ENTER PASSWORD
• ?
• SET OPTIONS NOECHO
• IDMS DC258003 V10 USER UCC7IDM SIGNED ON LTERM
  UCFL002 AT 015117.17 03.253
• V10 IDMSPR (MY) ENTER NEXT TASK CODE
• CHRF 20 30
  
  
  
• RF000003 RECOVERY FLAG IS ON FOR OFFLOADING
  JOURNAL J4JRNL
• RF000001 SAFE TO RESET RECOVERY FLAG ON J4JRNL
  
• V10 IDMSPR (MY) ENTER NEXT TASK CODE
• BYE
• 
  
• 
  

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Trivial functions

• Notes
• REXX code is very simple
• Would be possible to do the whole thing in REXX
• Allocate all necessary files
• Call UCFBATCH
• Process output
• Generate and submit Reset JCL

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Mundane functions

• DBA time is valuable shouldnt be wasted on
  functions which can be easily automated
• DBAN runs
• Backup scheduling/logging
• Health checking

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Mundane functions

• DBAN Runs
• CSS database too big to DBAN in one go
• No Read-only time to run DBANS anyway
• No space to copy whole database to
• DBAs could manually recover parts of database to
  copies, and then run DBANs

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Mundane functions

• REXX routine written to automate DBANs
• Parameter driven
• Areas to DBAN
• Volumes available to copy DB to, use for sort
  files etc
• JCL details (jobclass etc)

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Mundane functions

• REXX routines
• Read parameter files
• Build JCL to
• Delete old files
• Copy database files
• Recover files to a quiesce point (Cogitos SQP
  utility)
• Run DBN1 DBN2
• Check output from DBAN jobs

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Mundane functions

• Delete old files
• Generate list of files with name in format
  IDMSPR.DBAN.DFxxxxx'
• Build IEFBR14 job to delete these

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Mundane functions

• Copy database files
• Copy from IDMSPR.DFxxxxx to IDMSPR.DBAN.DFxxxxx

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Mundane functions

• Recover database files
• Read file containing SQP data
• Determine which journals to use for recovery
• Build JCL to
• Offload current journal if appropriate
• Rollback DBAN files to SQP

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Mundane functions

• Build JCL to run IDMSDBN1 IDMSDBN2
• Build JCL to check DBN2 output
• Update DBAN parameters

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Mundane functions

• In this way, the whole Database is DBANned
  without any DBA involvement
• Only notified if there are any problems
• Process is further parameter driven to allow
  COPYing of files, and CALS runs

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Mundane functions

• Also use REXX programs for
• Reorg functions, including in-flight resizing
• Building JCL
• Mapping new files onto existing volumes
• RACF/Security checking
• DB Summary reports

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Emergency functions

• Database recovery plans important to BT/CSS
• Hardware consolidation means up to10 CSS images
  on one physical machine
• Need to automate as much as possible, to relieve
  pressure on DBAs

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Emergency functions

• IARS
• IDMS Automated Recovery System
• Panels and REXX code to assist with IDMS recovery
• By File, Area or full Database
• 25,000 lines of REXX

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Emergency functions

• IARS automates all possible functions to recover
  a database
• Concatenate journals to use for recovery
• Builds all necessary JCL
• RollBack
• RollForward
• File allocation/formatting
• DBA simply runs through panels, and
  checks/submits JCL

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Emergency functions

• REXX execs will
• Drive whole recovery process via panels
• Constructs all needed JCL
• Determines which archive journals are needed for
  recovery
• As much as possible automated DBA free to
  concentrate on important issues

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Summary

• REXX is a powerful, flexible tool
• Used with standard/user-written utilities, it can
  greatly reduce a DBAs workload
• Automation of emergency procedures can reduce
  the risk of errors, and allow better use of DBAs
  time knowledge

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