Input Modules › Selective Retrieval of VSAM files (CULLVSAM) › Performing a Direct Read

Performing a Direct Read

To perform a direct read, code the following:

1. The INPUT parameter using the UM(CULLVSAM) option
2. REC parameters describing the VSAM file

   The start position of the VSAM record is relative to the beginning of the input buffer. The input buffer contains the entire key-file record followed by the VSAM record.

3. Type 7 logic (for key-sequenced files) to compare key file values to the key value of the retrieved VSAM record
4. The VSAM and key file assignment in the CA Culprit job control language:
   • The VSAM file is assigned to SYS010 in the CA Culprit JCL.

     If an alternate input file is required, it can be assigned with the DD= option on the INPUT parameter.

   • The sequential file containing key values (a key file) is assigned to SYS002.
5. A KEY control statement in the CULL step of the CA Culprit job control language. See the following "Coding the KEY control statement" for syntax.

Coding the KEY Control Statement for Direct Reads

To directly access specific records in the file, code the KEY control statement as shown below:

• Record-size-n, coded in columns 5 through 8, is a 4-digit number, that indicates the size of the key file record.
• F/V/U, coded in column 9, identifies the record type:

• Records-per-block-n, coded in columns 10 through 12, is a 3-digit number that indicates the number of records in each block on the key file.
• File-type-a, coded in column 13, is a 1-character code that defines the structure of the key file:

• Label-type-a, coded in column 14, is a 1-character code that specifies the label type of the key file:

• K/A is a 1-character keyword, coded in column 17, that identifies the VSAM file type:

• Start-position-n, coded in columns 22 through 25, is a 4-digit number that indicates the starting position of the key value on the key file record.
• Field-size-n, coded in columns 26 and 27, is a 2-digit number that indicates the length of the key field. When the key field size on the key file is less than the length of the VSAM key, the key file value is padded with binary zeros on the right.

Notes

• If the file is password protected, it cannot be opened without a valid password. Use PW= as the first control statement or omit the PW= statement and allow the console operator to supply the password.
• If a match between keys on the VSAM file and the key file cannot be made, CULLVSAM will return the record with the next higher key.
• If a record with the next higher key does not exist, CULLVSAM will return two asterisks (**) to the first two positions of the VSAM area in the CA Culprit input buffer.

Example

This example retrieves selected records directly from a variable-length KSDS file.

The following code uses:

• An INPUT parameter that specifies:
  • Variable-length records
  • A record size of 162 bytes, consisting of:
    • The key file record size (80 bytes)
    • The VSAM record size (80 bytes)
    • The record descriptor word (RDW) (2 bytes)
• A key control statement that describes the key file as:
  • A KSDS file having standard labels, 80-character fixed-length records, and a block size of one record
  • Having a key that is 4-bytes long and starts in position 1 of the key file
• Type 7 logic checks the key values of the key file and the VSAM record.

   IN 162 V 80 UM(CULLVSAM)
   REC KEYFILE-KEY   1   4  3
   REC NAME         81  16
   REC BALANCE      97   6  2  DP=2
   REC ACCOUNT     109   4  3
   013EXAMPLE OF CULLVSAM
   01410040 'DIRECT READ OF A VARIABLE LENGTH KEY-SEQUENCED FILE'
   0142*001 ' '
   0151*001 NAME             HH 'NAME'
   0151*002 BALANCE          HH 'BALANCE'
   0151*003 ACCOUNT      FN  HH 'ACCOUNT'
   0151*004 KEYFILE-KEY  FN  HH 'KEY FROM' 'KEYFILE'
   017      IF NAME EQ '**' DROP
   017      IF KEYFILE-KEY EQ ACCOUNT TAKE
   017      DROP
   01OUT  D
  //CULPRIT.VSAMCTRL DD *
   KEY0080F001   K  000104