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Understanding Token Numbers in XA Records

Understanding Token Numbers in XA Records. Tuesday, August 11, 2009 Presenter: Charles Hood, CISTECH, Inc. Overview. Purpose of XA Token Fields XA Files which use a Token Field Data Elements packed into a Token Calling the Token-Generator API Two “Gotchas”! “Potential” Duplicates

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Understanding Token Numbers in XA Records

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  1. Understanding Token Numbers in XA Records Tuesday, August 11, 2009 Presenter: Charles Hood, CISTECH, Inc.

  2. Overview • Purpose of XA Token Fields • XA Files which use a Token Field • Data Elements packed into a Token • Calling the Token-Generator API • Two “Gotchas”! • “Potential” Duplicates • Special R7 Consideration

  3. Purpose of XA Token Fields • To ensure that XA applications are able to obtain unique key access to application data that is not necessarily unique • Typically, master files have application data which ensures unique key access, but transaction files may not

  4. XA Files which use a Token Field (1) • Current list (subject to change in future releases) • MOMAST (token used in REP Schedules) • IMHIST • INVTXN • PCCTXN • OEITXN

  5. XA Files which use a Token Field (2) 6. SLQNTY 7. MOTRAN 8. ITMPRC 9. OPENAR 10. ARHSTS 11. PURACT

  6. Data Elements Packed into a Token (1) • Token fields are 15 character, alphanumeric • The “characters” in a Token field are hexadecimal values comprised of the following: • Date/Time • Sequence Number • System Job Number

  7. Data Elements Packed into a Token (2) • More detail: • Date/Time is 13 digits packed into 7 positions • Sequence Number is 7 digits packed into 4 positions • System Job Number is 6 digits packed into 4 positions

  8. Data Elements Packed into a Token (3) • Sample token from an ITMPRC record: ØbÉdè| jß| (Value in file) 0887854 0001 0954 002144F 000F 019F (Dt/Tm) (Seq#)(Job#)

  9. Calling the Token-Generator API (1) • API Program AMVLN generates tokens to uniquely identify records • A call to AMVLN requires four parameters: • (I) Shutdown/process 8 chars • (O) Unique key token 15 chars • (O) Message ID 7 chars • (O) Message data 512 chars

  10. Calling the Token-Generator API (2) • Expected Values for the “Shutdown/process” Input Paramter: • *PRC = Process with no program shutdown • *PRC_SHT = Process and shutdown • *SHT = No processing, just shutdown program

  11. Calling the Token-Generator API (3) • Sample Call to AMVLN: C* CALL TOKEN GENERATOR PGM FOR TOKEN FOR SLQNTY C* C CLEARTKEN C CALL 'AMVLN' C PARM '*PRC 'SHD$P 8 C TKEN PARM *BLANKS TKEN$P 15 C PARM *BLANKS MGID$P 7 C PARM *BLANKS MGDT1P C* C WRITESLQNTYSQ

  12. Two “Gotchas”! (1) • First “Gotcha” is due to the ability of modern fast iSeries processors to process a high volume of transactions. • When a U-job was ended and restarted within one second, duplicate tokens were generated because the sequence # was not saved. • This was resolved with a Program fix: XAR6 PTF 6943 XAR7 PTF 3640

  13. Two “Gotchas”! (2) • Second “Gotcha” can occur when the iSeries system time is reset (DST, Sync with Atomic Clock, etc.) • When resetting the system time, be careful! • All U-jobs must be ended • HLDJOBQ to prevent U-jobs starting • Get a Dedicated XA system • The post backup procedure is the best place for nightly updating the system time

  14. “Potential” Duplicates • Currently, AMVLN could generate duplicate Tokens after one century of use • “Older” AMVLN could generate a duplicate key if system processing speed improves to the point that 9,999,999 records can be added to a file in one second • “Newer” AMVLN includes the millisecond value in the Sequence Number portion – a theoretical possibility of duplicates still exists

  15. Special R7 Consideration (1) • In most XA files which use tokens as key fields, the token field is 15 characters alphanumeric; in the R7 integrator, however, the token field is 30 characters, with a subtype of “Hex” • When a Business Object user exit is activated which uses a file containing a token field as a key field (like Item Location, which uses the SLQNTYL4 logical), the token comes into the user exit program as a 30 character alphanumeric field

  16. Special R7 Consideration (2) • XA provides an API program PSVCHS1R which will convert a “Hex” field to its alphanumeric equivalent • A call to PSVCHS1R requires five parameters: • (I) Perform process? 8 chars • (I) Shutdown program? 8 chars • (I) Hexadecimal value 128 chars • (O) Character value 64 chars • (O) Message ID 7 chars

  17. Special R7 Consideration (3) • Sample Call to PSVCHS1R : * - P#HXVL Value must be in X’cccc’ format c Eval p#HXVL = ‘X’’’ + uTKENLQ + ‘’’’ c Call ‘PSVCHS1R' c Parm ‘*YES’ P#PFPR 8 c Parm ‘*NO’ P#SHDN 8 c Parm P#HXVL 128 c Parm *blanks P#CHVL 64 c Parm *blanks P#MSID 7 * c Movel p#chvl keyfld 15 c slqnkey Chain SLQTNYL4

  18. THANK YOU! Charles Hood Charles.hood@cistech.net

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