Steps for obtaining component trace data with an external writer

You can use an external writer to obtain component trace data for TCP/IP stacks, packet trace, OMPROUTE, and Telnet.

Procedure

Perform the following steps to obtain component trace data with an external writer:

Enter the appropriate writer procedure in SYS1.PROCLIB, as shown in the following example. Use a separate external writer for each CTRACE component. You can have multiple procedures writing to as many as 16 TRCOUT files either on disk or tape.
```
//PTTCP  PROC
//* REFER:  SYS1.PROCLIB(PTTCP)
//* COMPID: OPER
//* DOC:    THIS PROCEDURE IS THE IPCS CTRACE1 EXTERNAL WRITER PROCEDURE.
//*         USED BY TCP/IP   .
//*
//IEFPROC  EXEC  PGM=ITTTRCWR,REGION=0K,TIME=1440
//* TIME=1440 to prevent S322 abends
//TRCOUT01 DD DSNAME=MEGA.IPCS.CTRACE1,UNIT=SYSDA,
//             VOL=SER=STORGE,
//             SPACE=(4096,(100,10),,CONTIG),DISP=(NEW,CATLG),
// DCB=(DSORG=PS)
//
```
Restrictions:
- Do not specify the DCB parameters RECFM, LRECL, and BLKSIZE. The external writer defaults to an optimal blocking factor.
- Do not specify the RLSE subparameter of the SPACE parameter. The output data sets are opened and closed more than once when GTF runs.
Start the external writer using the following command:
```
TRACE CT,WTRSTART=procedure_name,WRAP
```
Turn on the trace and connect the external writer to the component either by specifying the external writer name in the PARMLIB member, or by specifying the external writer name in the TRACE command. When starting TCP/IP, because the SYSTCPDA component has no PARMLIB member, the PARMLIB option is not applicable for SYSTCPDA. For example, TRACE CT,ON,COMP=SYSTCPDA,SUB=(TCPCS),PARM=CTIEZBDA is a valid command. The PARMLIB member can specify a new buffer size or the name or a writer. To turn the trace on and connect the external writer to the component using a PARMLIB member, add the following TRACEOPTS option to the PARMLIB member:
```
WTR(xxx)
```
where xxx is the procedure name of the external writer. Then use this PARMLIB member when starting the program (TCP/IP, OMPROUTE, TELNET, or the Resolver) or if the program is already executing, issue the following command:
```
TRACE CT,ON,COMP=component_name,SUB=(procedure_name),PARM=parmlib_member
```
To turn on the trace and connect the external writer without using the PARMLIB member, enter the following command:
```
TRACE CT,ON,COMP=component_name,SUB=(procedure_name)
```
When the system responds, enter the following command:
```
R n,WTR=procedure_name,END 
```
where n is the response number issued by the system. You can add options to the response. The options vary for each component name. See Formatting component traces for references to the component options.

Use the DISPLAY command to check the external writer status. Include a sublevel.

D TRACE,COMP=SYSTCPDA,SUB=(TCPCS2)                    
IEE843I 11.33.06  TRACE DISPLAY 099                   
        SYSTEM STATUS INFORMATION                               
 ST=(ON,0064K,00064K) AS=ON  BR=OFF EX=ON  MT=(ON,064K)         
  TRACENAME                                                     
  =========                                                     
  SYSTCPDA                                                      
                      MODE BUFFER HEAD SUBS                     
                      =====================                     
                      OFF         HEAD    2                     
     NO HEAD OPTIONS                                            
  SUBTRACE            MODE BUFFER HEAD SUBS                     
 -------------------------------------------------------------- 
  TCPCS2              ON   0016M                                
     ASIDS      *NONE*                                          
     JOBNAMES   *NONE*                                          
     OPTIONS    MINIMUM                                         
     WRITER     PTTCP

Tip: The external writer is active for packet and data.

Turn off the trace or disconnect the external writer. The following two commands disconnect from the external writer, while leaving the trace running internally.
```
TRACE CT,ON,COMP=component_name,SUB=(procedure_jobname)
```
When the system responds, enter the second command:
```
R nn,WTR=DISCONNECT,END
```
Stop the external writer using the following command:
```
TRACE CT,WTRSTOP=procedure_name
```