Title : DL/1 Index Locking Relief

Submitter : Neil Price
            TNT Express Worldwide
            Abeles Way
            Wolley Lane Industrial Estate
            Atherstone
            Warwickshire
            CV9 2RY

Phone : 01827-710624

Release Submitter Details - Y



The Problem :-

The key hashing technique used to generate PI (Program Isolation)
resource identifiers from index keys may generate synonyms for keys
longer than 4 bytes. This can lead to unwanted PI waits and even
deadlocks.


A Possible Solution :-

Changing the key field TYPE specification on the FIELD statement IN THE
INDEX DBD may reduce synonyms. TYPE=C (character) is the default;
TYPE=P (packed) operates as TYPE=X (hexadecimal) for any key value
which is not valid packed decimal. TYPE=X is likely to give the best
results unless the key is packed or is strictly upper case alphanumeric

E.G. for a HIDAM Primary Index Database

          DBD   NAME=IXDBDNM,ACCESS=INDEX
          DATASET DD1=IXDD1,DEVICE=3390,SIZE=4096
          SEGM  NAME=IXROOT,PARENT=0,BYTES=7
          FIELD NAME=(IXKEY,SEQ,U),BYTES=7,START=1,TYPE=X
          LCHILD NAME(DBROOT,DBDNAME),INDEX=ROOTKEY,PTR=SNGL
          DBDGEN
          FINISH
          END

Bibliography : SC26-4284 IMS/ESA V3 Utilities Reference
               DBSOURCE library, member DFSHASH0


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