IDMS & REXX in BT

1. IDMS & REXX in BT Iain Robertson IDMS DBA British Telecom iain.dk.robertson@bt.com

2. 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 DBA’s life easier.

3. CSS – some background • CSS – Customer Service System • BT’s 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

5. 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

6. REXX and CSS • REXX applications fall into 3 categories: • Automating trivial maintenance functions • Automating mundane DBA functions • Automating ‘emergency’ functions

7. REXX – brief introduction • Replacement for CLISTS • Can be executed in TSO, or via batch job

8. REXX – brief introduction • Stem variables • EXECIO command • String parsing • Linking to programs, with optional parameters

9. ‘Trivial’ functions • EXAMPLE: Analysing output from utility programs • Either user written programs, or CA-supplied utilities (IDMSBCF, UCFBATCH)

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

11. ‘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)

12. ‘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

13. ‘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 01:51:17.17 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

14. ‘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

15. ‘Mundane’ functions • DBA time is valuable – shouldn’t be wasted on functions which can be easily automated • DBAN runs • Backup scheduling/logging • ’Health checking’

16. ‘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

17. ‘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)

18. ‘Mundane’ functions • REXX routines: • Read parameter files • Build JCL to: • Delete old files • Copy database files • Recover files to a quiesce point (Cogito’s SQP utility) • Run DBN1 & DBN2 • Check output from DBAN jobs

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

20. ‘Mundane’ functions • Copy database files: • Copy from IDMSPR.DFxxxxx to IDMSPR.DBAN.DFxxxxx

21. ‘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

22. ‘Mundane’ functions • Build JCL to run IDMSDBN1 & IDMSDBN2 • Build JCL to check DBN2 output • Update DBAN parameters

23. ‘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

24. ‘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

25. ‘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

26. ‘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

27. ‘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

28. ‘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

29. Summary • REXX is a powerful, flexible tool • Used with standard/user-written utilities, it can greatly reduce a DBA’s workload • Automation of ‘emergency’ procedures can reduce the risk of errors, and allow better use of DBA’s time & knowledge

30. ?