IBM 5280 Programmer's Manual page 163

Relative, Sequential, and Transaction Data Set Organization
Table 2: OPEN Status Codes
Status Key COBOL Detected Error
00 No error detected
30 See table 7 for detailed explanations.
92
The file is already open
Attempt to open a file after previous open failed for non-resource reasons
File is locked
Second attempt to open a TRANSACTION I/O file.
93 Insufficient main storage for buffers
See table 7 for additional causes.
95
COBOL detected invalid file characteristics:
ASCII not configured in system; file is declared as ASCII.
COBOL record size not equal to record size allocated on diskette by
SYSLABEL.
For relative files, a delete character was not specified when the data set
was allocated.
See Table 7 for additional causes.
B- 2 IBM 5280 COBOL Programmer's Guide