Flowcharts for Sample Routines

The following information illustrates flowcharts and logic of nonstandard label processing routines. The logic is shown separately for routines receiving control from the open, close, EOV, or restart routines of the control program. Each block in each of the flowcharts is numbered; each number corresponds to an item in the lists of explanations that follow the figures.

Figure 1. General Flow of a Nonstandard Label Processing Routine After Receiving Control from the Open Routine.

Figure 2. General Flow of a Nonstandard Label Processing Routine After Receiving Control from the Close Routine

Figure 3. General Flow of a Nonstandard Label Processing Routine After Receiving Control from the EOV Routine

Explanation of Logic Blocks-Figures Figure 1, Figure 2, and Figure 3

1

The entry is in the form of an XCTL macro instruction issued by the control program.

2

Use the GETMAIN or STORAGE macro instruction to obtain virtual storage.

3

Use the store multiple (STM) instruction and then set a register to point 32 bytes past register 6 as described in Figure 1.

4

To locate the address of the DCB, use the contents of register 5 ( Figure 1). Set register 4 to the address of the work area pointed to by the table entry described in Figure 1. (For EOV, this register is already set.)

To determine if the DCB is to be processed, test bits 6 and 7 of the DCBOFLGS field of the DCB; if these bits are 1, the DCB is to be processed. (The symbolic names of all fields in the DCB are defined by the DCBD macro instruction.) The user's DCB is pointed to by the DXUDCBAD field on the combined work and control block area.

If a DCB in the CLOSE parameter list is not open at entry to CLOSE, it is not processed, and its entry is all zeros in the table pointed to by register 6 at entry.

5

To determine if a tape data set is being processed, test the UCB3TAPE field of the UCB; this bit is 1 for a tape data set. The symbolic names of all fields in the UCB are defined by the IEFUCBOB macro instruction. The address of the UCB is contained in the DXDEBUCB field of the DEB as defined by the IECDSECT macro instruction. Register 4 points to this IECDSECT area. (The IECDSECT macro is described in Mapping the Common Open, Close, EOV Work Area.)

6

If nonstandard labels have been specified, the JFCBLTYP field of the JFCB has a hexadecimal 04.

7

The final DCB entry in the list of DCB addresses contains a 1 in its high-order bit position.

8

Add 4 to the contents of register 5; add 8 to the contents of the register set in Step 3.

9

Set the high-order bit to 0 in the UCBDMCT field of the UCB.

10

To determine the type of I/O operation specified in the OPEN macro instruction, check the bit configuration of the high-order byte of the the DCB entry in the list of DCB addresses. The bit configuration for each type of I/O operation is shown below. (The high-order 4 bits correspond to the disposition of the data set; the low-order 4 bits correspond to the I/O operation itself. For example, the bit configuration x0110000 indicates a data set opened for input whose disposition is LEAVE.)

0	1	2	3	4	5	6	7	Bits
x	0	0	1	x	x	x	x	REREAD
x	0	1	1	x	x	x	x	LEAVE
x	0	0	0	x	x	x	x	Neither REREAD nor LEAVE

x	x	x	x	0	0	0	0	INPUT
x	x	x	x	1	1	1	1	OUTPUT or EXTEND
x	x	x	x	0	1	1	1	OUTIN or OUTINX
x	x	x	x	0	1	0	0	UPDAT
x	x	x	x	0	0	1	1	INOUT
x	x	x	x	0	0	0	1	RDBACK

11

If the high-order bit of the DCBOFLGS field of the DCB is 1, the data set mode is output; if this bit is 0, the data set mode is input. (The symbolic names of all fields in the DCB are defined by the DCBD macro instruction.)

12

You can position the tape if you have closed an input data set before all data has been read.

13

Move your CCW into the channel program area of the control program's work area. (The symbolic name of the first entry in the channel program area is DXCCW.) You can use the first six entries.

14

Issue an EXCP macro instruction specifying the address of the control program's IOB. (The symbolic name of the IOB is DXIOB.)

15

Techniques used to check for correct volume differ depending on the label formats used in the installation.

16

Label processing routines differ by label format.

17

Use this block for a write operation.

18

Issue an EXCP macro instruction specifying the address of the control program's IOB. (The symbolic name of the IOB is DXIOB.)

If the command is a rewind, use the compare and swap instructions to set the rewind-issued bit in the UCB (UCBREW) before issuing the EXCP.

If the command is a rewind-unload, use the compare and swap instructions to set the unit-not-ready bit in the UCB (UCBNRY) and zero out the UCB volume serial number field (UCBVOLI) after the channel program is complete.

19

Set the high-order bit to 1 in the UCBDMCT field of the UCB.

20

Use the load multiple (LM) instruction.

21

Use the FREEMAIN macro instruction to free the work area obtained in step 2.

22

Use the XCTL macro instruction, specifying the appropriate operand.

This coding sequence illustrates an exit from your routine. At entry to the module, register 4 contains the address of the control program's work area for a DCB. The code below represents a generic work area.

         USING     IECDSECT,4
         LR        1,SAVEBASE           put work area pointer in
*                                       register 1 for FREEMAIN
         LM        2,14,REGSAVE         restore caller registers
         FREEMAIN  R,LV=size,A=(1)
         BALR      15,0                 use 15 as temporary base
         USING     *,15
         MVC       0(8,6),MODNAME       module name to
*                                       open/close/EOV area
         LA        15,DXCCW12           use open work area
         XCTL      EPLOC=(6),SF=(E,(15))
MODNAME  DC        C'IGGxxxxx'

Figure 4. General Flow of a Nonstandard Label Processing Routine After Receiving Control from the Restart Routine

Explanation of Logic Blocks- Figure 4

1: The entry is in the form of an XCTL macro instruction issued by the control program.
2: Use the GETMAIN macro instruction to obtain virtual storage.
3: Use the store multiple (STM) instruction.
4: Move your CCW into the channel program area of the control program's work area. (The symbolic name of the first entry in the channel program area is RSCCW1.)
The control program provides the device modifier byte, RSDEBMOD, in the DEB portion of the restart work area. RSDEBMOD contains the mode-set command for the data portion of the tape. If your nonstandard labels are recorded in a mode different from the data, your NSL routine must set the device modifier byte (RSDEBMOD) to the density and recording technique of the labels. (See "Tape Characteristics" in z/OS V2R1.0 DFSMS Using Magnetic Tapes.)
5: Issue an EXCP macro instruction specifying the address of the control program's IOB. (The symbolic name of the IOB is RSIOB.)
6: Determine if an uncorrectable I/O error occurred. This can be any type of error that you do not want to accept.
7: Set the high-order bit to 1 in the TABTPLBL field of the table entry to indicate the I/O error.
8: Techniques used to check for correct volume differ depending on the label formats used in the installation. The volume serial number for the mounted volume is shown in the UCB.
9: Perform any necessary label processing and tape positioning.
10: Set the high-order bit to 1 in the UCBDMCT field of the UCB.
11: Use the load multiple (LM) instruction.
12: Use the FREEMAIN macro instruction to free the work area obtained in step 2.
13: Use the XCTL macro instruction. The following coding sequence illustrates an exit from your routine.

         LR        1,SAVEBASE           put work area pointer in
                                        register 1 for FREEMAIN
         LM        2,14,REGSAVE         restore caller registers
         FREEMAIN  R,LV=size,A=(1)
         BALR      15,0                 use 15 as temporary base
         USING     *,15
         L         1,4(,9)              put pointer to restart
                                        work area into register 1
         MVC       128(8,1),MODNAME     put module name in
                                        restart work area
         LA        15,120(,1)           set up XCTL
                                        parameter pointers
         LA        5,128(,1)            set up XCTL
                                        parameter pointers
         XCTL      EPLOC=(5),SF=(E,(15))
MODNAME  DC        C'IGC0K05B'