The message list contains individual messages that correspond to detected attention or error conditions. Bytes 16 through 19 of the message area header contain the location of the message list within the message area. If the message area header is not stored completely, (bit 0 of byte 0 is 0), the location of the message list is not provided.

In the message list, individual messages are stored as a contiguous string of variable-length records. Bytes 14 and 15 of the message area header contain the number of messages stored. Check for a nonzero stored message count before investigating the message list. However, messages may not be stored even if the ACB error flag byte contains a nonzero value and the message area header bit 0 of byte 0 is 1. For example, no messages will be stored if MLEN is not large enough to allow at least one message to be stored.

The following shows the format of the individual messages.

Bytes 0-1

Length of message (including these 2 bytes).

Byte 2

ACB error flag code corresponding to the error or attention condition represented by this message.

Byte 3

Function type code:

Specifies which dsname, if any, is stored in bytes 4 through 47 of the message:

X'00'

No dsname stored. Bytes 4-47 of the message contain binary zeros. The error attention condition is not clearly related to a component, or VSAM was unable to identify or obtain the cluster name of the component in error. This code is used only if the ddname of the ACB does not identify a valid DD statement, or VSAM was unable to obtain the dsname contained in the DD statement.

X'01'

dsname contained in DD statement is stored. The error or attention condition is not clearly related to a component, or VSAM was unable to identify or obtain the cluster name of the component in error.

X'02'

dsname (cluster name) of base cluster stored. Error occurred during an open or close for base cluster.

X'03'

dsname (cluster name) of alternate index component stored. Error occurred during open or close processing for alternate index component.

X'04'

dsname (cluster name) of member of upgrade set stored. Error occurred during open or close for this member of the upgrade set.

Bytes 4-47

Binary zeros (function type code=X'00') or a dsname as described by byte 3.

Bytes 0 and 1 of each message specify its actual length. Because messages vary in length, you need to know the actual length of each message to do your processing.

Byte 2 of the message contains the ACB error flag code; it does not indicate a dsname has been stored. Depending on the condition that raised the ACB error flag code, either no dsname or different types of dsnames (DD, base cluster, alternate index, or upgrade set member) may be stored. (The same condition may be detected both when opening the base cluster and when opening a member of the upgrade set. For example, an I/O error may occur when trying to obtain the dsname for the component in error.)

Bytes 4 through 47 of the message can contain a dsname, but not specify its type.

Only byte 3 of the message specifies if a dsname was stored and, if so, its type.