diff --git a/hapi-fhir-docs/src/main/resources/ca/uhn/hapi/fhir/changelog/5_5_0/2791-increase-identifier-length.yaml b/hapi-fhir-docs/src/main/resources/ca/uhn/hapi/fhir/changelog/5_5_0/2791-increase-identifier-length.yaml
new file mode 100644
index 00000000000..78dbbf1262e
--- /dev/null
+++ b/hapi-fhir-docs/src/main/resources/ca/uhn/hapi/fhir/changelog/5_5_0/2791-increase-identifier-length.yaml
@@ -0,0 +1,4 @@
+---
+type: change
+issue: 2791
+title: "Identifier maximum length increased from 200 to 500. This specifically applies to table HFJ_IDX_CMP_STRING_UNIQ."
diff --git a/hapi-fhir-docs/src/main/resources/ca/uhn/hapi/fhir/docs/server_jpa_mdm/mdm_rules.md b/hapi-fhir-docs/src/main/resources/ca/uhn/hapi/fhir/docs/server_jpa_mdm/mdm_rules.md
index 3075b67543d..50d5ac73fd7 100644
--- a/hapi-fhir-docs/src/main/resources/ca/uhn/hapi/fhir/docs/server_jpa_mdm/mdm_rules.md
+++ b/hapi-fhir-docs/src/main/resources/ca/uhn/hapi/fhir/docs/server_jpa_mdm/mdm_rules.md
@@ -165,7 +165,7 @@ then the above `candidateSearchParams` and `candidateFilterSearchParams` would r
 
 ### matchFields
 
-Once the match candidates have been found, they are then each compared to the incoming Patient resource.  This comparison is made across a list of `matchField`s.  Each matchField returns `true` or `false` indicating whether the candidate and the incoming Patient match on that field.   There are two types of matchFields: `matcher` and `similarity`.  `matcher` matchFields return a `true` or `false` directly, whereas `similarity` matchFields return a score between 0.0 (no match) and 1.0 (exact match) and this score is translated to a `true/false` via a `matchThreshold`.  E.g. if a `JARO_WINKLER` matchField is configured with a `matchThreshold` of 0.8 then that matchField will only return `true` if the `JARO_WINKLER` similarity evaluates to a score >= 8.0.
+Once the match candidates have been found, they are then each compared to the incoming Patient resource.  This comparison is made across a list of `matchField`s.  Each matchField returns `true` or `false` indicating whether the candidate and the incoming Patient match on that field.   There are two types of matchFields: `matcher` and `similarity`.  `matcher` matchFields return a `true` or `false` directly, whereas `similarity` matchFields return a score between 0.0 (no match) and 1.0 (exact match) and this score is translated to a `true/false` via a `matchThreshold`.  E.g. if a `JARO_WINKLER` matchField is configured with a `matchThreshold` of 0.8 then that matchField will only return `true` if the `JARO_WINKLER` similarity evaluates to a score >= 0.8.
 
 By default, all matchFields have `exact=false` which means that they will have all diacritical marks removed and all letters will be converted to upper case before matching.  `exact=true` can be added to any matchField to compare the strings as they are originally capitalized and accented.
 
diff --git a/hapi-fhir-jpaserver-migrate/src/main/java/ca/uhn/fhir/jpa/migrate/tasks/HapiFhirJpaMigrationTasks.java b/hapi-fhir-jpaserver-migrate/src/main/java/ca/uhn/fhir/jpa/migrate/tasks/HapiFhirJpaMigrationTasks.java
index e25b83b4a55..0818e4109b7 100644
--- a/hapi-fhir-jpaserver-migrate/src/main/java/ca/uhn/fhir/jpa/migrate/tasks/HapiFhirJpaMigrationTasks.java
+++ b/hapi-fhir-jpaserver-migrate/src/main/java/ca/uhn/fhir/jpa/migrate/tasks/HapiFhirJpaMigrationTasks.java
@@ -99,6 +99,9 @@ public class HapiFhirJpaMigrationTasks extends BaseMigrationTasks<VersionEnum> {
 
 		version.onTable("HFJ_BLK_EXPORT_JOB")
 			.modifyColumn("20210624.1","REQUEST").nonNullable().withType(ColumnTypeEnum.STRING, 1024);
+
+		version.onTable("HFJ_IDX_CMP_STRING_UNIQ")
+			.modifyColumn("20210713.1","IDX_STRING").nonNullable().withType(ColumnTypeEnum.STRING, 500);
 	}
 
 	private void init540() {
diff --git a/hapi-fhir-jpaserver-model/src/main/java/ca/uhn/fhir/jpa/model/entity/ResourceIndexedCompositeStringUnique.java b/hapi-fhir-jpaserver-model/src/main/java/ca/uhn/fhir/jpa/model/entity/ResourceIndexedCompositeStringUnique.java
index 50b6161c55b..05d093c6c65 100644
--- a/hapi-fhir-jpaserver-model/src/main/java/ca/uhn/fhir/jpa/model/entity/ResourceIndexedCompositeStringUnique.java
+++ b/hapi-fhir-jpaserver-model/src/main/java/ca/uhn/fhir/jpa/model/entity/ResourceIndexedCompositeStringUnique.java
@@ -37,7 +37,7 @@ import javax.persistence.*;
 })
 public class ResourceIndexedCompositeStringUnique extends BasePartitionable implements Comparable<ResourceIndexedCompositeStringUnique> {
 
-	public static final int MAX_STRING_LENGTH = 200;
+	public static final int MAX_STRING_LENGTH = 500;
 	public static final String IDX_IDXCMPSTRUNIQ_STRING = "IDX_IDXCMPSTRUNIQ_STRING";
 	public static final String IDX_IDXCMPSTRUNIQ_RESOURCE = "IDX_IDXCMPSTRUNIQ_RESOURCE";