Hi,

According to the DFSMS Using Dataset manual, the following is specified in the "Access to records through alternate indexes":

Each record in the data component of an alternate index is of variable length and contains header data,
the alternate key, and at least one pointer to a base data record. Header data is fixed length and provides
the following information:
• Whether the alternate index data record contains primary keys or RBA pointers.
• Whether the alternate index data record contains unique or nonunique keys.
• The length of each pointer.
• The length of the alternate key.
• The number of pointers.

The following is the breakdown of the five-byte header:

• Whether the alternate index data record contains primary keys or RBA pointers. High order bits in Byte 1 - 0: primary keys 1: RBA

• Whether the alternate index data record contains unique or nonunique keys. Low order bits in Byte 1 - 0: No duplicates, 1: Duplicates

• The length of each pointer. Byte 2

• The length of the alternate key. Byte 5

• The number of pointers. Bytes 3,4

All of them are accurate except for the no duplicates/duplicates indicator.

Any help is deeply appreciated.

Hi,

According to the DFSMS Using Dataset manual, the following is specified in the "Access to records through alternate indexes":

Each record in the data component of an alternate index is of variable length and contains header data,
the alternate key, and at least one pointer to a base data record. Header data is fixed length and provides
the following information:
• Whether the alternate index data record contains primary keys or RBA pointers.
• Whether the alternate index data record contains unique or nonunique keys.
• The length of each pointer.
• The length of the alternate key.
• The number of pointers.

The following is the breakdown of the five-byte header:

• Whether the alternate index data record contains primary keys or RBA pointers. High order bits in Byte 1 - 0: primary keys 1: RBA

• Whether the alternate index data record contains unique or nonunique keys. Low order bits in Byte 1 - 0: No duplicates, 1: Duplicates

• The length of each pointer. Byte 2

• The length of the alternate key. Byte 5

• The number of pointers. Bytes 3,4

All of them are accurate except for the no duplicates/duplicates indicator.

Any help is deeply appreciated.

Hello Girish,

So I've looked back in history (as far as I can go) and it doesn't look like we have ever had a bit to describe unique or non-unique in that structure, probably because if the number of pointers is greater than 1, you know it is not unique.  I appreciate you pointing that out and I will request the documentation be clarified. 

Was there some reason you were looking for that information?

Regards,

Helen Witter

Hi,

According to the DFSMS Using Dataset manual, the following is specified in the "Access to records through alternate indexes":

Each record in the data component of an alternate index is of variable length and contains header data,
the alternate key, and at least one pointer to a base data record. Header data is fixed length and provides
the following information:
• Whether the alternate index data record contains primary keys or RBA pointers.
• Whether the alternate index data record contains unique or nonunique keys.
• The length of each pointer.
• The length of the alternate key.
• The number of pointers.

The following is the breakdown of the five-byte header:

• Whether the alternate index data record contains primary keys or RBA pointers. High order bits in Byte 1 - 0: primary keys 1: RBA

• Whether the alternate index data record contains unique or nonunique keys. Low order bits in Byte 1 - 0: No duplicates, 1: Duplicates

• The length of each pointer. Byte 2

• The length of the alternate key. Byte 5

• The number of pointers. Bytes 3,4

All of them are accurate except for the no duplicates/duplicates indicator.

Any help is deeply appreciated.

Hi,

There is a production job that monitors the space usage of AIX.  In automating it we tried using the header information to check only AIX that allowed duplicates - over 100 of them.  Anyhow, we ended up using the "UNIQUE" option to define the AIX that had no duplicates and used the information in the LISTCAT to select the AIX that could hold duplicates.

Thank you.

Hello Girish,

So I've looked back in history (as far as I can go) and it doesn't look like we have ever had a bit to describe unique or non-unique in that structure, probably because if the number of pointers is greater than 1, you know it is not unique.  I appreciate you pointing that out and I will request the documentation be clarified. 

Was there some reason you were looking for that information?

Regards,

Helen Witter

Hi,

According to the DFSMS Using Dataset manual, the following is specified in the "Access to records through alternate indexes":

Each record in the data component of an alternate index is of variable length and contains header data,
the alternate key, and at least one pointer to a base data record. Header data is fixed length and provides
the following information:
• Whether the alternate index data record contains primary keys or RBA pointers.
• Whether the alternate index data record contains unique or nonunique keys.
• The length of each pointer.
• The length of the alternate key.
• The number of pointers.

The following is the breakdown of the five-byte header:

• Whether the alternate index data record contains primary keys or RBA pointers. High order bits in Byte 1 - 0: primary keys 1: RBA

• Whether the alternate index data record contains unique or nonunique keys. Low order bits in Byte 1 - 0: No duplicates, 1: Duplicates

• The length of each pointer. Byte 2

• The length of the alternate key. Byte 5

• The number of pointers. Bytes 3,4

All of them are accurate except for the no duplicates/duplicates indicator.

Any help is deeply appreciated.