Conversation Level Pacing

To control the amount of buffer space available to any one conversation, use the CONVBUFF parameter in the APPC start procedure in SYS1.PROCLIB. Specify the amount of buffer space in kilobytes. Use one of the following methods:

Specify a value for the for the CONVBUFF parameter on the PROC statement. For example, if you want to set 2000 kilobytes as the maximum amount of buffer space that any one conversation can use at one time, specify the following:
```
//     APPC PROC APPC=00,CONVBUFF=2000
```
In the EXEC statement, set CONVBUFF=&CONVBUFF, as follows:
```
//     EXEC  PGM=ATBINITM,PARM='APPC=&APPC,CONVBUFF=&CONVBUFF...'
```
If you use this method, you can specify CONVBUFF=xx on the START APPC command to change the CONVBUFF value.
Define a fixed value for the CONVBUFF parameter on the EXEC statement. For example, if you want to set 2000 kilobytes as the maximum amount of buffer space that any one conversation can use at one time, specify the following:
```
//     EXEC  PGM=ATBINITM,PARM='APPC=&APPC,CONVBUFF=2000...'
```
Let APPC/MVS use the default value for CONVBUFF, which is 1000 kilobytes. Code the exec statement as follows:
```
//     EXEC  PGM=ATBINITM,PARM='APPC=&APPC...'
```

When specifying the amount of buffer space available to any one conversation on the CONVBUFF parameter, keep the following in mind:

The maximum value you can specify is 2097152 kilobytes (decimal).
If you do not specify a value, or if you specify a value of zero, APPC/MVS uses the default value of 1000 kilobytes.
If you specify a value between 1 and 39 on the CONVBUFF parameter, the system uses a value of 40 (because APPC/MVS requires a minimum of 40 kilobytes of storage per conversation).
If you specify a value that is not a multiple of four kilobytes (decimal), the system rounds the value of CONVBUFF up to the next highest multiple of four. For example, if you specify CONVBUFF=1023, the system makes 1024 kilobytes of buffer storage available to one conversation.
If you specify a value on CONVBUFF that is greater than the buffer storage limit (which is either the default value calculated by APPC/MVS or the value specified on the BUFSTOR parameter), the system does the following:
- Issues message ATB017I
- Uses the buffer storage limit.
For example, the system performs the actions listed above if you enter the following command (which specifies a CONVBUFF value that is greater than the BUFSTOR value):
```
S APPC,SUB=MSTR,BUFSTOR=8,CONVBUFF=2097148
```