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DM API METHODS AND PROPERTIES 201

GetNextKey

Most of the tables in the DM SQL database have a SYSTEM_ID column

as their primary key. DM generates primary key values for new rows in

those tables by calling the GetNextKey method with no input

parameter. Primary key values that are generated with no input

parameter receive their key value from the

TBNAME column that has a

value of

SYSTEMKEY. Because so many tables obtain their primary key

values from this pool of numbers, the generic name of

SYSTEMKEY is

used. There is no

SYSTEMKEY table.

You are not required to store primary key values generated in this

manner—with no input parameter—in a column named

SYSTEM_ID.

For example, the

LOOKUPS table uses the METHODNUM column as its

primary key, but it is generated in the same manner as other tables that

use the more common

SYSTEM_ID column as a primary key. You can

do the same thing with tables that your custom applications require,

whether you name your primary key column

SYSTEM_ID or something

different.

Some DM SQL database tables maintain primary keys that do not

generate key values by incrementing the

SYSTEMKEY column value.

One example of this occurs in the

PROFILE table where the DOCNUMBER

column is shown as an “alternate” primary key. DM uses this primary

key to manage the Document File Store, where the actual document

content resides. You will see this in the

DOCS_UNIQUE_KEYS table with

its

TBNAME column set to “DOCSADM.PROFILE”.

As a developer using the DM API to create your customized

applications or enhancements to the basic product, you have complete

flexibility to manage primary keys for the tables you create. You can

maintain separate key entries in the

DOCS_UNIQUE_KEYS table for the

tables you create, or you can retrieve key values from the

SYSTEMKEY

pool that DM supports. With a maximum key value in excess of 2

billion, neither the

SYSTEMKEY nor other DOCS_UNIQUE_KEYS table

entries are likely to exhaust the available pool of key values.

Note: Oracle supports system-generated sequences through use of a

CREATE SEQUENCE SQL statement. DM uses this instead of the

DOCS_UNIQUE_KEYS table to manage primary key values in Oracle

databases. These columns are stored in the DUAL table. The previous

discussion of primary key usage is all relevant to Oracle users, with the

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