diff --git a/src/Platforms/DB2Platform.php b/src/Platforms/DB2Platform.php
index b92cbd684b4..dc35f7458a0 100644
--- a/src/Platforms/DB2Platform.php
+++ b/src/Platforms/DB2Platform.php
@@ -25,6 +25,25 @@
 
 class DB2Platform extends AbstractPlatform
 {
+    /** @see https://www.ibm.com/docs/en/db2/11.5?topic=views-syscatcolumns */
+    private const SYSCAT_COLUMNS_GENERATED_DEFAULT = 'D';
+
+    /** @see https://www.ibm.com/docs/en/db2/11.5?topic=views-syscatindexes */
+    private const SYSCAT_INDEXES_UNIQUERULE_PERMITS_DUPLICATES     = 'D';
+    private const SYSCAT_INDEXES_UNIQUERULE_IMPLEMENTS_PRIMARY_KEY = 'P';
+
+    /** @see https://www.ibm.com/docs/en/db2/11.5?topic=views-syscattabconst */
+    private const SYSCAT_TABCONST_TYPE_PRIMARY_KEY = 'P';
+
+    /** @see https://www.ibm.com/docs/en/db2/11.5?topic=views-syscatreferences */
+    private const SYSCAT_REFERENCES_UPDATERULE_RESTRICT = 'R';
+    private const SYSCAT_REFERENCES_DELETERULE_CASCADE  = 'C';
+    private const SYSCAT_REFERENCES_DELETERULE_SET_NULL = 'N';
+    private const SYSCAT_REFERENCES_DELETERULE_RESTRICT = 'R';
+
+    /** @see https://www.ibm.com/docs/en/db2-for-zos/11?topic=tables-systables */
+    private const SYSIBM_SYSTABLES_TYPE_TABLE = 'T';
+
     /**
      * {@inheritdoc}
      *
@@ -362,14 +381,14 @@ public function getListTableColumnsSQL($table, $database = null)
                  c.remarks AS comment,
                  k.colseq,
                  CASE
-                 WHEN c.generated = 'D' THEN 1
+                 WHEN c.generated = '" . self::SYSCAT_COLUMNS_GENERATED_DEFAULT . "' THEN 1
                  ELSE 0
                  END     AS autoincrement
                FROM syscat.columns c
                  LEFT JOIN (syscat.keycoluse k JOIN syscat.tabconst tc
                      ON (k.tabschema = tc.tabschema
                          AND k.tabname = tc.tabname
-                         AND tc.type = 'P'))
+                         AND tc.type = '" . self::SYSCAT_TABCONST_TYPE_PRIMARY_KEY . "'))
                    ON (c.tabschema = k.tabschema
                        AND c.tabname = k.tabname
                        AND c.colname = k.colname)
@@ -391,7 +410,8 @@ public function getListTableColumnsSQL($table, $database = null)
      */
     public function getListTablesSQL()
     {
-        return "SELECT NAME FROM SYSIBM.SYSTABLES WHERE TYPE = 'T' AND CREATOR = CURRENT_USER";
+        return "SELECT NAME FROM SYSIBM.SYSTABLES WHERE TYPE = '" . self::SYSIBM_SYSTABLES_TYPE_TABLE . "'"
+            . ' AND CREATOR = CURRENT_USER';
     }
 
     /**
@@ -416,11 +436,13 @@ public function getListTableIndexesSQL($table, $database = null)
         return "SELECT   idx.INDNAME AS key_name,
                          idxcol.COLNAME AS column_name,
                          CASE
-                             WHEN idx.UNIQUERULE = 'P' THEN 1
+                             WHEN idx.UNIQUERULE = '" . self::SYSCAT_INDEXES_UNIQUERULE_IMPLEMENTS_PRIMARY_KEY . "'
+                             THEN 1
                              ELSE 0
                          END AS primary,
                          CASE
-                             WHEN idx.UNIQUERULE = 'D' THEN 1
+                             WHEN idx.UNIQUERULE = '" . self::SYSCAT_INDEXES_UNIQUERULE_PERMITS_DUPLICATES . "'
+                             THEN 1
                              ELSE 0
                          END AS non_unique
                 FROM     SYSCAT.INDEXES AS idx
@@ -444,13 +466,13 @@ public function getListTableForeignKeysSQL($table)
                          pkcol.COLNAME AS foreign_column,
                          fk.CONSTNAME AS index_name,
                          CASE
-                             WHEN fk.UPDATERULE = 'R' THEN 'RESTRICT'
+                             WHEN fk.UPDATERULE = '" . self::SYSCAT_REFERENCES_UPDATERULE_RESTRICT . "' THEN 'RESTRICT'
                              ELSE NULL
                          END AS on_update,
                          CASE
-                             WHEN fk.DELETERULE = 'C' THEN 'CASCADE'
-                             WHEN fk.DELETERULE = 'N' THEN 'SET NULL'
-                             WHEN fk.DELETERULE = 'R' THEN 'RESTRICT'
+                             WHEN fk.DELETERULE = '" . self::SYSCAT_REFERENCES_DELETERULE_CASCADE . "' THEN 'CASCADE'
+                             WHEN fk.DELETERULE = '" . self::SYSCAT_REFERENCES_DELETERULE_SET_NULL . "' THEN 'SET NULL'
+                             WHEN fk.DELETERULE = '" . self::SYSCAT_REFERENCES_DELETERULE_RESTRICT . "' THEN 'RESTRICT'
                              ELSE NULL
                          END AS on_delete
                 FROM     SYSCAT.REFERENCES AS fk