Buffer Size Control

To control the buffer limit size, use the BUFSTOR parameter in the APPC start procedure in SYS1.PROCLIB. Specify the buffer storage limit in megabytes. Use one of the following methods:

Specify the buffer storage limit of 88 megabytes used for MVS/ESA SP 4.2, if it is appropriate for your system. (The BUFSTOR parameter was not available in MVS/ESA SP 4.2, so systems were required to use the default buffer storage limit of 88 megabytes for that release.) Set BUFSTOR=88 in the PROC statement:
```
//     APPC PROC APPC=00,BUFSTOR=88
```
In the EXEC statement, set BUFSTOR=&BUFSTOR, as follows:
```
//     EXEC  PGM=ATBINITM,PARM='APPC=&APPC,BUFSTOR=&BUFSTOR...'
```
If you use this method, you can specify BUFSTOR=xx on the START APPC command to change the BUFSTOR value.
Define a fixed value for the BUFSTOR parameter, from 0 to 2048, on the EXEC statement. For example, if you want to set 48 megabytes as the buffer storage limit, specify the following:
```
//     EXEC  PGM=ATBINITM,...PARM='APPC=&APPC,BUFSTOR=48'
```
Let APPC/MVS calculate a value based on your auxiliary storage. If you do not include the BUFSTOR parameter in the EXEC statement, APPC/MVS calculates a value that is approximately one third of the amount of free auxiliary storage your system has at the time APPC starts.
```
//     EXEC  PGM=ATBINITM,PARM='APPC=&APPC...'
```
Each time the operator enters the START APPC command, the system re-calculates the buffer storage limit value.

When specifying the buffer storage limit on the BUFSTOR parameter, keep the following in mind:

The value must be a decimal value between 0 and 2048. If you specify 0 or a value greater than 2048, the system sets the buffer storage limit to the maximum of 2048.
If you specify a value less than or equal to 8, the system uses a value of 8. If you specify a value greater than 8, the system rounds the value down to the nearest multiple of 8.
If you use a constant buffer storage limit value, you might want to calculate it from an RMF page/swap data set activity report taken at a peak period. Use numbers from the report in the following equations:
```
 # available slots = (# slots allocated) - (max slots used)

 MB of available storage = (# available slots)/256
```
Your buffer storage limit value should not exceed the MB of available storage that results from the second equation.