DB01001W PXX AREA FULL occurs frequently

Products

• Datacom/DB
• Datacom/AD
• Datacom

Issue/Introduction

The Datacom PXX becomes full very frequently during overnight batch run.

DB01001W - PXX AREA FULL

When it becomes full DBUTLTY is run to clear it with:

COMM OPTION=CLRPXX

What is the appropriate PXX size to reduce the number of times PXX Full occurs?

Environment

Release: 15.1

Resolution

The size of the PXX can be increaseas required without causing any problem. It can be increased gradually until it no longer becomes full.
However, the current recommendation is not to use the PXX, instead specify the MUF Startup Option SYSOUT. 

This directs most output that would normally go to the PXX to go to dynamically allocated SYSOUT datasets. See article PXX vs SYSOUT Datacom MUF Startup Option for more details.

Also specify JCL PARM NO_PXX in the MUF EXEC statement so the PXX will not be allocated to the MUF. See documentation section Modify MUF JCL Parameters.

This also requires that MUF startup option PXXSTATS EOJPRT be specified. With this option, the  summary statistics are written to the MUF EOJ report and not to the PXX. See documentation section PXXSTATS.

The reason the PXX is filling up in this case is that startup option PXXSTATS DETAIL has been specified.
This will generate a large amount of statistics and written to the PXX. Unless actively monitoring the MUF, it is not recommended to specify PXXSTATS DETAIL because it can cause performance issues. It should be changed to specify PXXSTATS EOJPRT.
See documentation section PXXSTATS:

Only specify DETAIL or allow the default if you want MUF statistics to be written to the PXX at every URT close. This makes the information available for printing with the DBUTLTY function REPORT AREA=PXX,SYSSTATS=. Writing the information requires one through many synchronous I/O events to the PXX data set. Because most users do not choose to view or analyze this information, the accompanying overhead to the MUF can be saved by not specifying DETAIL. The information is available on demand for SQL users or SYSVIEW users by using the Dynamic System Table MUF_SYSTEM_STATS (MFS).

For most users not actively using detail information for tuning the MUF, we recommend that you specify either PXXSTATS=EOJ or PXXSTATS=EOJPRT as the most efficient choices. Either one prevents the PXX from filling with information that is probably only rarely going to be viewed.