CXXMAINT (Maintain Directory) › CXXMAINT ALTER OPTION2= (Activating Other Features) › CXXMAINT ALTER OPTION2=datafs (DATAFS Support) › How to Use

How to Use

To use the DATA FAST SEARCH option, use the following command:

►►─ CXXMAINT OPTION=ALTER,OPTION2=datafs ─────────────────────────────────────►◄

Command

CXXMAINT

Invokes the function for Directory maintenance.

Required Keywords

OPTION=ALTER

Requests the CXXMAINT ALTER option.

,OPTION2=datafs

Indicates whether to use the DATAFS search algorithm for performance enhanced searching of multi-table areas and areas with tables that use compression.

Specify datafs as N_DATAFS when you do not want to use DATAFS.

Specify datafs as Y_DATAFS when you want to use DATAFS. When the DATAFS feature has been turned on, each data block in a Unique Row Identifier (URI) area is eligible to use the new algorithm that includes altering the DASD for a given block. A URI is a sequential number assigned when a row is added or inserted that CA Datacom/DB uses to identify a row. Areas which qualified for using the binary search algorithm in previous releases continue to use the previous algorithm. Each data block uses the new DATAFS approach if there are a sufficient number of rows in the block to make the new approach worthwhile.

Once the global DATAFS option is turned on, blocks have the new search criteria built in one of two ways.

• The search criteria is built and stored at the end of the data block if, as rows are added to new or existing blocks, the search criteria has not yet been built, there are a sufficient number of rows in the block, and the block currently has at least 16 bytes of space available at the end.
• The DBUTLTY function RETIX,AREA=*DATA builds the search criteria if DATAFS is set to Y for URI data areas that are not using the old style binary search. Since this DBUTLTY already runs in MUF, it allows sites with existing populated URI data areas to build the search criteria in MUF (and on DASD) without taking an area offline. For each individual data block, however, the search criteria can be built only if there are 16 bytes available at the end of the block.

Because the new DATAFS algorithm needs the last 16 bytes of each data block, it is possible for each existing data area to require more physical DASD space. This includes all methods of newly populating a data area (LOAD, and so on), or inserting rows in an existing data area. There are two exceptions: RECOVERY and LOAD from a RECID backup using data from before DATAFS is set to Y. In these two cases, physical data placement takes precedence over the 16 bytes used by DATAFS.

Valid Entries:

Y_DATAFS or N_DATAFS

Default Value:

(No default)