DFS0451I modname, dbdname, ddname, i/o error, decb field
or
hhmmss, variable text
Explanation
Any of the forms of this message can be issued. A READ or a WRITE error has occurred during an I/O operation.
Module modname detected an error during an I/O operation or while processing the write error queue elements (WEQE) for the identified ddname in database dbdname. The variable i/o error indicates whether it is a READ error or whether a WEQE is found, and the status code is returned to the application program. No status code is returned for the WRITE error.
If the access method is VSAM, this message is preceded by a display of bytes 26-125 of the VSAM physical error message, prefixed by DFS0451I hhmmss. For the format and contents of this message, see z/OS® DFSMS Macro Instructions for Data Sets.
If the access method is OSAM, decb field is the field DECBSTAT from the DECB used for the I/O operation, followed by a description of the error. See message DFS0762I for the DECB status code (DECBSTAT) definitions.
If the access method is OSAM and the data set is defined as a VSAM linear data set, decb field will be “21-MM” followed by a return code from Media Manager. See the Media Manager Diagnostic Aids for a description of the return code.
If the IOEROPN=(n,WTOR) parameter is specified when the PSB is generated and if the system is batch (DLI or DBB), the operator can specify abend or continue. This option is only specified in batch for an action-required message.
- modname
- One of the following modules issued the message:
- DFSDVSM0
- DFSDBH00
- DFSDBHM0
- DFSDDLE0
- dbdname
- Database name
- ddname
- DD name
- i/o error
- Indicates that a READ or WRITE error has occurred during an I/O operation or that the WEQE
(write error queue element) was detected. Whenever a WRITE error has occurred and the subsystem does
not have a copy of the data, a WEQE is created for the block.
If an application requests data in a block with a WEQE, this message is generated and a status code is passed back to the application program. After the database recovery has been performed, all WEQEs for the database will be freed. The WEQE in the subsystem incurring the WRITE error (data sharing or non-data sharing environment) is flagged to allow error free READ operations for that block in that subsystem. In a data sharing environment, if an application running in a subsystem other than the one incurring the WRITE error requests a segment in the given database block, this message is generated and a status code is passed back to the application program. A READ operation is not issued for the block since it was incorrect. After the database recovery has been performed, all WEQEs for the database will be freed. In a nondata sharing environment, if the database is closed and then reused without recovering it (for example /DBD instead of /DBR), this flag is removed and subsequent READ requests for that block result in this message being issued.
- decb field
- A DECB field is indicated by the DECBSTAT or DECBEXC
For the hhmmss, variable text version:
A READ or a WRITE error has occurred during an I/O operation. This form of the message is issued for VSAM errors. hhmmss is a time stamp, and variable text is from VSAM.
The VSAM error IEQE indicates the existence of a key-sequenced data set (KSDS) IO toleration extended error queue element (EEQE) to prevent any access to the record pointed by the EEQE.
System action
For the action-required message, DL/I waits for the operator to respond before continuing. If the operator responds with ABEND, the application program terminates with pseudoabend 0451, and IMS continues processing. However, if DUMP=YES was specified on the DL/I buffer options statement, the application terminates with standard abend 0451. An operator response of CONT causes IMS to continue processing.
For the information message, processing continues.
If IOEROPN=(451,WTOR), IMS terminates with abend 0451, even if the operator responds CONT to the DFS0451A message.
Operator response
(system): For the action-required message, reply ABEND to cause abend 0451, or CONT to cause IMS to continue processing. No action is required for the information message.(master terminal) : Contact the appropriate support personnel responsible for the recovery of the database.
System programmer response
For both messages, if it is a permanent READ error or WRITE error, recover the database. However, if only WRITE errors occur, the database might continue to be used by the online system, and recovery can be delayed until a convenient time. If application performance is affected or READ errors occur, the database must be recovered.