IMS DB - SSA

SSA stands for Segment Search Arguments. SSA is used to identify the segment occurrence being accessed. It is an optional parameter. We can include any number of SSAs depending on the requirement. There are two types of SSAs −

Unquapfied SSA

Quapfied SSA

Unquapfied SSA

An unquapfied SSA provides the name of the segment being used inside the call. Given below is the syntax of an unquapfied SSA −

01 UNQUALIFIED-SSA.
   05  SEGMENT-NAME  PIC X(8).
   05  FILLER        PIC X     VALUE SPACE.

The key points of unquapfied SSA are as follows −

A basic unquapfied SSA is 9 bytes long.

The first 8 bytes hold the segment name which is being used for processing.

The last byte always contains space.

DL/I uses the last byte to determine the type of SSA.

To access a particular segment, move the name of the segment in the SEGMENT-NAME field.

The following images show the structures of unquapfied and quapfied SSAs −

Quapfied SSA

A Quapfied SSA provides the segment type with the specific database occurrence of a segment. Given below is the syntax of a Quapfied SSA −

01 QUALIFIED-SSA.
   05  SEGMENT-NAME  PIC X(8).
   05  FILLER        PIC X(01)     VALUE  ( .
   05  FIELD-NAME    PIC X(8).
   05  REL-OPR       PIC X(2).
   05  SEARCH-VALUE  PIC X(n).
   05  FILLER        PIC X(n+1) VALUE  ) .

The key points of quapfied SSA are as follows −

The first 8 bytes of a quapfied SSA holds the segment name being used for processing.

The ninth byte is a left parenthesis ( .

The next 8 bytes starting from the tenth position specifies the field name which we want to search.

After the field name, in the 18^th and 19^th positions, we specify two-character relational operator code.

Then we specify the field value and in the last byte, there is a right parenthesis ) .

The following table shows the relational operators used in a Quapfied SSA.

Command Codes

Command codes are used to enhance the functionapty of DL/I calls. Command codes reduce the number of DL/I calls, making the programs simple. Also, it improves the performance as the number of calls is reduced. The following image shows how command codes are used in unquapfied and quapfied SSAs −

The key points of command codes are as follows −

To use command codes, specify an asterisk in the 9^th position of the SSA as shown in the above image.

Command code is coded at the tenth position.

From 10^th position onwards, DL/I considers all characters to be command codes until it encounters a space for an unquapfied SSA and a left parenthesis for a quapfied SSA.

The following table shows the pst of command codes used in SSA −

Multiple Quapfications

The fundamental points of multiple quapfications are as follows −

Multiple quapfications are required when we need to use two or more quapfications or fields for comparison.

We use Boolean operators pke AND and OR to connect two or more quapfications.

Multiple quapfications can be used when we want to process a segment based on a range of possible values for a single field.

Given below is the syntax of Multiple Quapfications −

01 QUALIFIED-SSA.
   05  SEGMENT-NAME  PIC X(8).
   05  FILLER        PIC X(01)     VALUE  ( .
   05  FIELD-NAME1   PIC X(8).
   05  REL-OPR       PIC X(2).
   05  SEARCH-VALUE1 PIC X(m).
   05  MUL-QUAL      PIC X      VALUE  & .
   05  FIELD-NAME2   PIC X(8).
   05  REL-OPR       PIC X(2).
   05  SEARCH-VALUE2 PIC X(n).
   05  FILLER        PIC X(n+1) VALUE  ) .

MUL-QUAL is a short term for MULtiple QUALIification in which we can provide boolean operators pke AND or OR.