Step 1: Create the initialization module

The initialization module is created using the EZACICR macro. A minimum of two invocations of the macro are coded and assembled and the assembly produces the module. An example follows:

          EZACICR TYPE=INITIAL
          EZACICR TYPE=FINAL

This produces an initialization module which creates one record of binary zeros. If you want to preload the file with dummy records for frequently referenced domain names, it resembles the following:

         EZACICR TYPE=INITIAL
         EZACICR TYPE=RECORD,NAME=HOSTA
         EZACICR TYPE=RECORD,NAME=HOSTB
         EZACICR TYPE=RECORD,NAME=HOSTC
         EZACICR TYPE=FINAL

where HOSTA, HOSTB, AND HOSTC are the host names you want in the dummy records. The names can be specified in any order.

The specifications for the EZACICR macro are as follows:

Operand

Meaning

TYPE

There are three acceptable values:

Value: Meaning
INITIAL: Indicates the beginning of the generation input. This value should appear only once and should be the first entry in the input stream.
RECORD: Indicates a dummy record the user wants to generate. There can be from 0 to 4096 dummy records generated and each of them must have a unique name. Generating dummy records for frequently used host names improves the performance of the cache file. A TYPE=INITIAL must precede a TYPE=RECORD statement.
FINAL: Indicates the end of the generation input. This value should appear only once and should be the last entry in the input stream. A TYPE=INITIAL must precede a TYPE=FINAL.

AVGREC

The length of the average cache record. This value is specified on the TYPE=INITIAL macro and has a default value of 500. Use the default value until you have adequate statistics to determine a better value. This parameter is the same as the first subparameter in the RECORDSIZE parameter of the IDCAMS DEFINE statement. Accurate definition of this parameter along with use of dummy records minimizes control interval and control area splits in the cache file.

NAME

Specifies the host name for a dummy record. The name must be from 1 to 255 bytes long. The NAME operand is required for TYPE=RECORD entries.

The macro can be used in conjunction with IDCAMS to define and load the file. The following example shows a sample job to define and initialize a cache file:

Figure 1. Example of defining and initializing a DNS cache file

//CACHEDEF JOB (accounting,information),programmer.name,
//             MSGLEVEL=(1,1),MSGCLASS=A,CLASS=A
//*
//*   z/OS Communications Server
//*   SMP/E distribution name: EZACICFG
//*
//*   Licensed Materials - Property of IBM
//*   "Restricted Materials of IBM"
//*   5694-A01
//*   Copyright IBM Corp. 2000,2008
//*
//*   Status = CSV1R10
//*
//*   Function: This job defines and then loads the VSAM
//*   file used for the CICS TCP cache.  The job stream
//*   has the following steps:
//*
//*   1.  Delete a cache file if one exists
//*   2.  Define the VSAM cache file to VSAM
//*   3.  Assemble the initialization program
//*   4.  Link the initialization program
//*   5.  Execute the initialization program to load the
//*       VSAM cache file
//*
//* THIS STEP DELETES AN OLD COPY OF THE FILE
//* IF ONE IS THERE.
//*
//DEL    EXEC  PGM=IDCAMS
//SYSPRINT DD  SYSOUT=*
//SYSIN    DD  *
   DELETE -
      CICS.USER.CACHE -
      PURGE -
      ERASE
//*
//* THIS STEP DEFINES THE NEW FILE
//*
//DEFINE EXEC  PGM=IDCAMS
//SYSPRINT DD  SYSOUT=*
//SYSIN    DD  *
  DEFINE CLUSTER (NAME(CICS.USER.CACHE) VOLUMES(CICVOL) -
      CYL(1 1) -
      RECORDSIZE(500 1000) FREESPACE(0 15) -
      INDEXED ) -
      DATA ( -
        NAME(CICS.USER.CACHE.DATA) -
        KEYS (255 0) ) -
      INDEX ( -
        NAME(CICS.USER.CACHE.INDEX) )
/*
//*
//* THIS STEP DEFINES THE FILE LOAD PROGRAM
//*
//ASM      EXEC  PGM=ASMA90,PARM='OBJECT,TERM',REGION=1024K
//SYSLIB   DD  DISP=SHR,DSNAME=SYS1.MACLIB
//         DD  DISP=SHR,DSNAME=TCPV34.SEZACMAC
//SYSUT1   DD  UNIT=SYSDA,SPACE=(CYL,(5,1))
//SYSUT2   DD  UNIT=SYSDA,SPACE=(CYL,(2,1))
//SYSUT3   DD  UNIT=SYSDA,SPACE=(CYL,(2,1))
//SYSPUNCH DD  DISP=SHR,DSNAME=NULLFILE
//SYSLIN   DD  DSNAME=&&OBJSET,DISP=(MOD,PASS),UNIT=SYSDA,
//             SPACE=(400,(500,50)),
//             DCB=(RECFM=FB,BLKSIZE=400,LRECL=80)
//SYSTERM  DD  SYSOUT=*
//SYSPRINT DD  SYSOUT=*
//SYSIN    DD  *
        EZACICR TYPE=INITIAL
        EZACICR TYPE=RECORD,NAME=RALVM12
        EZACICR TYPE=FINAL
/*
//LINK   EXEC  PGM=IEWL,PARM='LIST,MAP,XREF',
//             REGION=512K,COND=(4,LT,ASM)
//SYSPRINT DD  SYSOUT=*
//SYSUT1   DD  SPACE=(CYL,(5,1)),DISP=(NEW,PASS),UNIT=SYSDA
//SYSLMOD  DD  DSNAME=&&LOADSET(GO),DISP=(MOD,PASS),UNIT=SYSDA,
//             SPACE=(TRK,(1,1,1)),
//             DCB=(DSORG=PO,RECFM=U,BLKSIZE=32760)
//SYSLIN   DD  DSNAME=&&OBJSET,DISP=(OLD,DELETE)
//*
//* THIS STEP EXECUTES THE FILE LOAD PROGRAM
//*
//LOAD   EXEC  PGM=*.LINK.SYSLMOD,
//             COND=((4,LT,DEFINE),(4,LT,ASM),(4,LT,LINK))
//EZACICRF DD  DSN=CICS.USER.CACHE,DISP=OLD

After the cache file has been created, it has the following layout:

Field name: Description
Host name: A 255-byte character field specifying the host name. This field is the key to the file.
Record type: A 1-byte binary field specifying the record type. The value is X'00000001'.
Last refresh time: An 8-byte packed field specifying the last refresh time. It is expressed in seconds because 0000 hours on January 1, 1990 and is derived by taking the ABSTIME value obtained from an EXEC CICS® ASKTIME and subtracting the value for January 1, 1990.
Offset to alias pointer list: A halfword binary field specifying the offset in the record to DNSALASA.
Number of INET addresses: A halfword binary field specifying the number of INET addresses in DNSINETA.
INET addresses: One or more fullword binary fields specifying INET addresses returned from GETHOSTBYNAME().
Alias names: An array of variable length character fields specifying the alias names returned from the name server cache. These fields are delimited by a byte of binary zeros. Each of these fields have a maximum length of 255 bytes.