diff --git a/defaults/solr.collection.schema b/defaults/solr.collection.schema
index 48fff9136..edf3a72a8 100644
--- a/defaults/solr.collection.schema
+++ b/defaults/solr.collection.schema
@@ -24,6 +24,9 @@ dates_in_content_dts
 ## the number of entries in dates_in_content_sxt
 dates_in_content_count_i
 
+## time when resource was loaded
+load_date_dt
+
 ## content of itemprop attributes with content='startDate'
 startDates_dts
 
@@ -42,17 +45,11 @@ www_unique_b
 ## content of title tag, text (mandatory field)
 title
 
-## the 64 bit hash of the org.apache.solr.update.processor.Lookup3Signature of title, used to compute title_unique_b
-#title_exact_signature_l
-
-## flag shows if title is unique within all indexable documents of the same host with status code 200; if yes and another document appears with same title, the unique-flag is set to false, boolean
-#title_unique_b
-
 ## id of the host, a 6-byte hash that is part of the document id (mandatory field)
 host_id_s
 
-## the md5 of the raw source
-#md5_s
+## host of the url, string
+host_s
 
 ## the 64 bit hash of the org.apache.solr.update.processor.Lookup3Signature of text_t
 exact_signature_l
@@ -60,21 +57,12 @@ exact_signature_l
 ## flag shows if exact_signature_l is unique at the time of document creation, used for double-check during search
 exact_signature_unique_b
 
-## counter for the number of documents which are not unique (== count of not-unique-flagged documents + 1)
-#exact_signature_copycount_i
-
 ## 64 bit of the Lookup3Signature from EnhancedTextProfileSignature of text_t
 fuzzy_signature_l
-
-## intermediate data produced in EnhancedTextProfileSignature: a list of word frequencies
-#fuzzy_signature_text_t
     
 ## flag shows if fuzzy_signature_l is unique at the time of document creation, used for double-check during search
 fuzzy_signature_unique_b
 
-## counter for the number of documents which are not unique (== count of not-unique-flagged documents + 1)
-#fuzzy_signature_copycount_i
-
 ## the size of the raw source (mandatory field)
 size_i
 
@@ -87,9 +75,6 @@ failtype_s
 ## html status return code (i.e. "200" for ok), -1 if not loaded (see content of failreason_t for this case), int (mandatory field)
 httpstatus_i
 
-## redirect url if the error code is 299 < httpstatus_i < 310
-#httpstatus_redirect_s
-
 ## number of unique http references, should be equal to references_internal_i + references_external_i
 references_i
 
@@ -105,18 +90,64 @@ references_exthosts_i
 ## crawl depth of web page according to the number of steps that the crawler did to get to this document; if the crawl was started at a root document, then this is equal to the clickdepth
 crawldepth_i
 
+## key from a harvest process (i.e. the crawl profile hash key) which is needed for near-realtime postprocessing. This shall be deleted as soon as postprocessing has been terminated.
+harvestkey_s
+
+## the file name extension
+url_file_ext_s
+
+## either the second level domain or, if a ccSLD is used, the third level domain. Needed to search in the url
+host_organization_s
+
+## internal links, only the protocol. Needed for HostBrowser
+inboundlinks_protocol_sxt
+
+## internal links, the url only without the protocol. For correct assembly of inboundlinks  inboundlinks_protocol_sxt + inboundlinks_urlstub_sxt is needed
+inboundlinks_urlstub_sxt
+
+## external links, only the protocol. For correct assembly of outboundlinks  outboundlinks_protocol_sxt + outboundlinks_urlstub_sxt is needed
+outboundlinks_protocol_sxt
+
+## external links, the url only without the protocol. Needed to enhance the crawler
+outboundlinks_urlstub_sxt
+
+## all image links without the protocol and '://'. For correct assembly of image url  images_protocol_sxt + images_urlstub_sxt is needed
+images_urlstub_sxt
+
+## all image link protocols
+images_protocol_sxt
+
+
+### No more mandatory (have been mandatory in some older YaCy versions)
+
+## the 64 bit hash of the org.apache.solr.update.processor.Lookup3Signature of title, used to compute title_unique_b
+#title_exact_signature_l
+
+## flag shows if title is unique within all indexable documents of the same host with status code 200; if yes and another document appears with same title, the unique-flag is set to false, boolean
+#title_unique_b
+
+## the md5 of the raw source
+#md5_s
+
+## counter for the number of documents which are not unique (== count of not-unique-flagged documents + 1)
+#exact_signature_copycount_i
+
+## intermediate data produced in EnhancedTextProfileSignature: a list of word frequencies
+#fuzzy_signature_text_t
+
+## counter for the number of documents which are not unique (== count of not-unique-flagged documents + 1)
+#fuzzy_signature_copycount_i
+
+## redirect url if the error code is 299 < httpstatus_i < 310
+#httpstatus_redirect_s
+
 ## needed (post-)processing steps on this metadata set
 #process_sxt
 
-## key from a harvest process (i.e. the crawl profile hash key) which is needed for near-realtime postprocessing. This shall be deleted as soon as postprocessing has been terminated.
-harvestkey_s
 
 
 ### optional but highly recommended values, part of the index distribution process
 
-## time when resource was loaded
-load_date_dt
-
 ## date until resource shall be considered as fresh
 fresh_date_dt
 
@@ -260,21 +291,9 @@ h6_txt
 ## content of <meta name="generator" content=#content#> tag, text
 #metagenerator_t
 
-## internal links, only the protocol
-inboundlinks_protocol_sxt
-
-## internal links, the url only without the protocol
-inboundlinks_urlstub_sxt
-
 ## internal links, the visible anchor text
 inboundlinks_anchortext_txt
 
-## external links, only the protocol
-outboundlinks_protocol_sxt
-
-## external links, the url only without the protocol
-outboundlinks_urlstub_sxt
-
 ## external links, the visible anchor text
 outboundlinks_anchortext_txt
 
@@ -293,12 +312,6 @@ icons_sizes_sxt
 ## all text/words appearing in image alt texts or the tokenized url
 images_text_t
 
-## all image links without the protocol and '://'
-images_urlstub_sxt
-
-## all image link protocols
-images_protocol_sxt
-
 ## all image link alt tag
 images_alt_sxt
 
@@ -416,9 +429,6 @@ url_file_name_s
 ## tokens generated from url_file_name_s which can be used for better matching and result boosting
 #url_file_name_tokens_t
 
-## the file name extension
-url_file_ext_s
-
 ## number of all path elements in the url hpath (see: http://www.ietf.org/rfc/rfc1738.txt) without the file name
 url_paths_count_i
     
@@ -437,15 +447,9 @@ url_paths_sxt
 ## number of all characters in the url == length of sku field
 url_chars_i
 
-## host of the url, string
-host_s
-
 ## the Domain Class Name, either the TLD or a combination of ccSLD+TLD if a ccSLD is used.
 #host_dnc_s
     
-## either the second level domain or, if a ccSLD is used, the third level domain
-host_organization_s
-    
 ## the organization and dnc concatenated with '.'
 #host_organizationdnc_s
     
diff --git a/htroot/IndexSchema_p.html b/htroot/IndexSchema_p.html
index b47c920de..9a747bf3b 100644
--- a/htroot/IndexSchema_p.html
+++ b/htroot/IndexSchema_p.html
@@ -44,8 +44,8 @@
       </tr>
       #{schema}#
       <tr class="TableCell#(dark)#Light::Dark::Summary#(/dark)#">
-        <td align="center"><input type="checkbox" name="schema_#[key]#" value="checked" #(checked)#::checked="checked"#(/checked)#/></td>
-        <td align="left">#[key]#</td>
+        <td align="center"><input type="checkbox" id="schema_#[key]#" name="schema_#[key]#" value="checked" #(checked)#::checked="checked"#(/checked)# #(required)#::required="required"#(/required)#/></td>
+        <td align="left"><label for="schema_#[key]#">#(required)#::<strong>#(/required)##[key]##(required)#::</strong>#(/required)#</label></td>
         <td align="left"><input type="text" name="schema_solrfieldname_#[key]#" value="#[solrfieldname]#"/></td>
         <td align="left">#[comment]#</td>
       </tr>
diff --git a/htroot/IndexSchema_p.java b/htroot/IndexSchema_p.java
index 15d78e1b0..5482bf05a 100644
--- a/htroot/IndexSchema_p.java
+++ b/htroot/IndexSchema_p.java
@@ -119,6 +119,7 @@ public class IndexSchema_p {
             if (showline) {
                 prop.put("schema_" + c + "_dark", dark ? 1 : 0); dark = !dark;
                 prop.put("schema_" + c + "_checked", cs.contains(field.name()) ? 1 : 0);
+                prop.put("schema_" + c + "_required", field.isMandatory() ? 1 : 0);
                 prop.putHTML("schema_" + c + "_key", field.name());
                 prop.putHTML("schema_" + c + "_solrfieldname",field.name().equalsIgnoreCase(field.getSolrFieldName()) ? "" : field.getSolrFieldName());
                 if (field.getComment() != null) prop.putHTML("schema_" + c + "_comment",field.getComment());
diff --git a/source/net/yacy/cora/federate/solr/SchemaDeclaration.java b/source/net/yacy/cora/federate/solr/SchemaDeclaration.java
index 94f7f9da2..179e8b84e 100644
--- a/source/net/yacy/cora/federate/solr/SchemaDeclaration.java
+++ b/source/net/yacy/cora/federate/solr/SchemaDeclaration.java
@@ -33,7 +33,10 @@ public interface SchemaDeclaration {
      */
     public String name(); // default field name (according to SolCell default schema) <= enum.name()
     
-    public String getSolrFieldName(); // return the default or custom solr field name to use for solr requests
+    /**
+     * @return the default or custom solr field name to use for solr requests
+     */
+    public String getSolrFieldName();
 
     public SolrType getType();
 
@@ -51,6 +54,11 @@ public interface SchemaDeclaration {
 
     public String getComment();
 
+    /**
+     * @return true when this field is mandatory for proper operation
+     */
+    public boolean isMandatory();
+
     public void setSolrFieldName(String name);
 
     public void add(final SolrInputDocument doc, final String value);
diff --git a/source/net/yacy/cora/federate/solr/connector/EmbeddedSolrConnector.java b/source/net/yacy/cora/federate/solr/connector/EmbeddedSolrConnector.java
index bfde578b9..a874c6bf3 100644
--- a/source/net/yacy/cora/federate/solr/connector/EmbeddedSolrConnector.java
+++ b/source/net/yacy/cora/federate/solr/connector/EmbeddedSolrConnector.java
@@ -420,7 +420,7 @@ public class EmbeddedSolrConnector extends SolrServerConnector implements SolrCo
     /**
      * check if a given document, identified by url hash as document id exists
      * @param id the url hash and document id
-     * @return the load date if any entry in solr exists, -1 otherwise
+     * @return the load date if any entry in solr exists, null otherwise
      * @throws IOException
      */
     @Override
diff --git a/source/net/yacy/search/Switchboard.java b/source/net/yacy/search/Switchboard.java
index 1265086f2..e0986331f 100644
--- a/source/net/yacy/search/Switchboard.java
+++ b/source/net/yacy/search/Switchboard.java
@@ -102,7 +102,6 @@ import net.yacy.cora.document.id.DigestURL;
 import net.yacy.cora.document.id.MultiProtocolURL;
 import net.yacy.cora.federate.solr.FailCategory;
 import net.yacy.cora.federate.solr.Ranking;
-import net.yacy.cora.federate.solr.SchemaConfiguration;
 import net.yacy.cora.federate.solr.connector.ShardSelection;
 import net.yacy.cora.federate.solr.connector.SolrConnector.LoadTimeURL;
 import net.yacy.cora.federate.solr.instance.RemoteInstance;
@@ -488,29 +487,6 @@ public final class Switchboard extends serverSwitch {
             // update the working scheme with the backup scheme. This is necessary to include new features.
             // new features are always activated by default (if activated in input-backupScheme)
             solrCollectionConfigurationWork.fill(solrCollectionConfigurationInit, true);
-            // switch on some fields which are necessary for ranking and faceting
-            SchemaConfiguration.Entry entry;
-            for (CollectionSchema field: new CollectionSchema[]{
-                    CollectionSchema.host_s, CollectionSchema.load_date_dt,
-                    CollectionSchema.url_file_ext_s, CollectionSchema.last_modified,                      // needed for media search and /date operator
-                    /*YaCySchema.url_paths_sxt,*/ CollectionSchema.host_organization_s,                   // needed to search in the url
-                    /*YaCySchema.inboundlinks_protocol_sxt,*/ CollectionSchema.inboundlinks_urlstub_sxt,  // needed for HostBrowser
-                    /*YaCySchema.outboundlinks_protocol_sxt,*/ CollectionSchema.outboundlinks_urlstub_sxt,// needed to enhance the crawler
-                    CollectionSchema.httpstatus_i                                                         // used in all search queries to filter out error documents
-                }) {
-                entry = solrCollectionConfigurationWork.get(field.name());
-                if (entry != null) {
-                    entry.setEnable(true);
-                    solrCollectionConfigurationWork.put(field.name(), entry);
-                }
-            }
-            
-            // activate some fields that are necessary here
-            entry = solrCollectionConfigurationWork.get(CollectionSchema.images_urlstub_sxt.getSolrFieldName());
-            if (entry != null) {
-                entry.setEnable(true);
-                solrCollectionConfigurationWork.put(CollectionSchema.images_urlstub_sxt.getSolrFieldName(), entry);
-            }
             solrCollectionConfigurationWork.commit();
         } catch (final IOException e) {ConcurrentLog.logException(e);}
         
diff --git a/source/net/yacy/search/schema/CollectionConfiguration.java b/source/net/yacy/search/schema/CollectionConfiguration.java
index 8dd70ae28..c08d65cdf 100644
--- a/source/net/yacy/search/schema/CollectionConfiguration.java
+++ b/source/net/yacy/search/schema/CollectionConfiguration.java
@@ -150,6 +150,7 @@ public class CollectionConfiguration extends SchemaConfiguration implements Seri
                 ConcurrentLog.warn("SolrCollectionWriter", " solr schema file " + configurationFile.getAbsolutePath() + " is missing declaration for '" + field.name() + "'");
         	}
         }
+        checkMandatoryFields(); // Check minimum needed fields for proper operation are enabled
         checkFieldRelationConsistency();
     }
 
@@ -183,6 +184,27 @@ public class CollectionConfiguration extends SchemaConfiguration implements Seri
             this.put(CollectionSchema.images_protocol_sxt.name(), e);
         }
     }
+    
+    /**
+     * Check and update schema configuration with fields strictly needed for proper YaCy operation.
+     */
+    private void checkMandatoryFields() {
+        SchemaConfiguration.Entry entry;
+        for (CollectionSchema field: CollectionSchema.values()) {
+        	if(field.isMandatory()) {
+        		entry = this.get(field.name());
+            	if (entry != null) {
+            		if(!entry.enabled()) {
+            			entry.setEnable(true);
+            			ConcurrentLog.info("SolrCollectionWriter", "Forced activation of mandatory field " + field.name());
+            		}
+            	} else {
+            		this.put(field.name(), new Entry(field.name(), field.getSolrFieldName(), true));
+            		ConcurrentLog.info("SolrCollectionWriter", "Added missing mandatory field " + field.name());
+            	}
+        	}
+        }
+    }
 
     public String[] allFields() {
         ArrayList<String> a = new ArrayList<>(this.size());
@@ -215,6 +237,7 @@ public class CollectionConfiguration extends SchemaConfiguration implements Seri
      */
     @Override
     public void commit() throws IOException {
+    	checkMandatoryFields(); // Check minimum needed fields for proper operation are enabled
         checkFieldRelationConsistency(); // in case of changes, check related fields are enabled before save
         try {
             super.commit();
diff --git a/source/net/yacy/search/schema/CollectionSchema.java b/source/net/yacy/search/schema/CollectionSchema.java
index 1b5e84b3b..642f92d5e 100644
--- a/source/net/yacy/search/schema/CollectionSchema.java
+++ b/source/net/yacy/search/schema/CollectionSchema.java
@@ -31,44 +31,55 @@ import org.apache.solr.common.SolrInputDocument;
 public enum CollectionSchema implements SchemaDeclaration {
     
     // mandatory
-    id(SolrType.string, true, true, false, false, false, "primary key of document, the URL hash **mandatory field**"),
-    sku(SolrType.string, true, true, false, true, true, "url of document"), // a 'sku' is a stock-keeping unit, a unique identifier and a default field in unmodified solr.
+    id(SolrType.string, true, true, false, false, false, "primary key of document, the URL hash **mandatory field**", true),
+    sku(SolrType.string, true, true, false, true, true, "url of document", true), // a 'sku' is a stock-keeping unit, a unique identifier and a default field in unmodified solr.
     //sku(SolrType.text_en_splitting_tight, true, true, false, true, true, "url of document"), // a 'sku' is a stock-keeping unit, a unique identifier and a default field in unmodified solr.
-    last_modified(SolrType.date, true, true, false, false, false, "last-modified from http header"), // date document was last modified
-    dates_in_content_dts(SolrType.date, true, true, true, false, true, "if date expressions can be found in the content, these dates are listed here as date objects in order of the appearances"),
-    dates_in_content_count_i(SolrType.num_integer, true, true, false, false, false, "the number of entries in dates_in_content_sxt"),
-    startDates_dts(SolrType.date, true, true, true, false, true, "content of itemprop attributes with content='startDate'"),
-    endDates_dts(SolrType.date, true, true, true, false, true, "content of itemprop attributes with content='endDate'"),
-    content_type(SolrType.string, true, true, true, false, false, "mime-type of document"),
-    http_unique_b(SolrType.bool, true, true, false, false, false, "unique-field which is true when an url appears the first time. If the same url which was http then appears as https (or vice versa) then the field is false"),
-    www_unique_b(SolrType.bool, true, true, false, false, false, "unique-field which is true when an url appears the first time. If the same url within the subdomain www then appears without that subdomain (or vice versa) then the field is false"),
-    title(SolrType.text_general, true, true, true, false, true, "content of title tag"),
+    last_modified(SolrType.date, true, true, false, false, false, "last-modified from http header", true), // date document was last modified, needed for media search and /date operator
+    dates_in_content_dts(SolrType.date, true, true, true, false, true, "if date expressions can be found in the content, these dates are listed here as date objects in order of the appearances", true),
+    dates_in_content_count_i(SolrType.num_integer, true, true, false, false, false, "the number of entries in dates_in_content_sxt", true),
+    load_date_dt(SolrType.date, true, true, false, false, false, "time when resource was loaded", true),
+    startDates_dts(SolrType.date, true, true, true, false, true, "content of itemprop attributes with content='startDate'", true),
+    endDates_dts(SolrType.date, true, true, true, false, true, "content of itemprop attributes with content='endDate'", true),
+    content_type(SolrType.string, true, true, true, false, false, "mime-type of document", true),
+    http_unique_b(SolrType.bool, true, true, false, false, false, "unique-field which is true when an url appears the first time. If the same url which was http then appears as https (or vice versa) then the field is false", true),
+    www_unique_b(SolrType.bool, true, true, false, false, false, "unique-field which is true when an url appears the first time. If the same url within the subdomain www then appears without that subdomain (or vice versa) then the field is false", true),
+    title(SolrType.text_general, true, true, true, false, true, "content of title tag", true),
+    host_id_s(SolrType.string, true, true, false, false, false, "id of the host, a 6-byte hash that is part of the document id", true),// String hosthash();
+    host_s(SolrType.string, true, true, false, false, true, "host of the url", true),
+    exact_signature_l(SolrType.num_long, true, true, false, false, false, "the 64 bit hash of the org.apache.solr.update.processor.Lookup3Signature of text_t", true),
+    exact_signature_unique_b(SolrType.bool, true, true, false, false, false, "flag shows if exact_signature_l is unique at the time of document creation, used for double-check during search", true),
+    fuzzy_signature_l(SolrType.num_long, true, true, false, false, false, "64 bit of the Lookup3Signature from EnhancedTextProfileSignature of text_t", true),
+    fuzzy_signature_unique_b(SolrType.bool, true, true, false, false, false, "flag shows if fuzzy_signature_l is unique at the time of document creation, used for double-check during search", true),
+    size_i(SolrType.num_integer, true, true, false, false, false, "the size of the raw source", true),// int size();
+    failreason_s(SolrType.string, true, true, false, false, false, "fail reason if a page was not loaded. if the page was loaded then this field is empty", true),
+    failtype_s(SolrType.string, true, true, false, false, false, "fail type if a page was not loaded. This field is either empty, 'excl' or 'fail'", true),
+    httpstatus_i(SolrType.num_integer, true, true, false, false, false, "html status return code (i.e. \"200\" for ok), -1 if not loaded", true),
+    references_i(SolrType.num_integer, true, true, false, false, false, "number of unique http references, should be equal to references_internal_i + references_external_i", true),
+    references_internal_i(SolrType.num_integer, true, true, false, false, false, "number of unique http references from same host to referenced url", true),
+    references_external_i(SolrType.num_integer, true, true, false, false, false, "number of unique http references from external hosts", true),
+    references_exthosts_i(SolrType.num_integer, true, true, false, false, false, "number of external hosts which provide http references", true),
+    crawldepth_i(SolrType.num_integer, true, true, false, false, false, "crawl depth of web page according to the number of steps that the crawler did to get to this document; if the crawl was started at a root document, then this is equal to the clickdepth", true),
+    harvestkey_s(SolrType.string, true, true, false, false, false, "key from a harvest process (i.e. the crawl profile hash key) which is needed for near-realtime postprocessing. This shall be deleted as soon as postprocessing has been terminated.", true),
+    url_file_ext_s(SolrType.string, true, true, false, false, true, "the file name extension", true),
+    host_organization_s(SolrType.string, true, true, false, false, true, "either the second level domain or, if a ccSLD is used, the third level domain", true), // needed to search in the url
+    inboundlinks_urlstub_sxt(SolrType.string, true, true, true, false, true, "internal links, the url only without the protocol", true), // needed for HostBrowser
+    inboundlinks_protocol_sxt(SolrType.string, true, true, true, false, false, "internal links, only the protocol", true), // for correct assembly of inboundlinks  inboundlinks_protocol_sxt + inboundlinks_urlstub_sxt is needed
+    outboundlinks_protocol_sxt(SolrType.string, true, true, true, false, false, "external links, only the protocol", true), // for correct assembly of outboundlinks  outboundlinks_protocol_sxt + outboundlinks_urlstub_sxt is needed
+    outboundlinks_urlstub_sxt(SolrType.string, true, true, true, false, true, "external links, the url only without the protocol", true), // needed to enhance the crawler
+    images_urlstub_sxt(SolrType.string, true, true, true, false, true, "all image links without the protocol and '://'", true),
+    images_protocol_sxt(SolrType.string, true, true, true, false, false, "all image link protocols", true), // for correct assembly of image url  images_protocol_sxt + images_urlstub_sxt is needed
+    
+    // no more mandatory (have been mandatory in some older YaCy versions)
     title_exact_signature_l(SolrType.num_long, true, true, false, false, false, "the 64 bit hash of the org.apache.solr.update.processor.Lookup3Signature of title, used to compute title_unique_b"),
     title_unique_b(SolrType.bool, true, true, false, false, false, "flag shows if title is unique within all indexable documents of the same host with status code 200; if yes and another document appears with same title, the unique-flag is set to false"),
-    host_id_s(SolrType.string, true, true, false, false, false, "id of the host, a 6-byte hash that is part of the document id"),// String hosthash();
     md5_s(SolrType.string, true, true, false, false, false, "the md5 of the raw source"),// String md5();
-    exact_signature_l(SolrType.num_long, true, true, false, false, false, "the 64 bit hash of the org.apache.solr.update.processor.Lookup3Signature of text_t"),
-    exact_signature_unique_b(SolrType.bool, true, true, false, false, false, "flag shows if exact_signature_l is unique at the time of document creation, used for double-check during search"),
     exact_signature_copycount_i(SolrType.num_integer, true, true, false, false, false, "counter for the number of documents which are not unique (== count of not-unique-flagged documents + 1)"),
-    fuzzy_signature_l(SolrType.num_long, true, true, false, false, false, "64 bit of the Lookup3Signature from EnhancedTextProfileSignature of text_t"),
     fuzzy_signature_text_t(SolrType.text_general, true, true, false, false, true, "intermediate data produced in EnhancedTextProfileSignature: a list of word frequencies"),
-    fuzzy_signature_unique_b(SolrType.bool, true, true, false, false, false, "flag shows if fuzzy_signature_l is unique at the time of document creation, used for double-check during search"),
     fuzzy_signature_copycount_i(SolrType.num_integer, true, true, false, false, false, "counter for the number of documents which are not unique (== count of not-unique-flagged documents + 1)"),
-    size_i(SolrType.num_integer, true, true, false, false, false, "the size of the raw source"),// int size();
-    failreason_s(SolrType.string, true, true, false, false, false, "fail reason if a page was not loaded. if the page was loaded then this field is empty"),
-    failtype_s(SolrType.string, true, true, false, false, false, "fail type if a page was not loaded. This field is either empty, 'excl' or 'fail'"),
-    httpstatus_i(SolrType.num_integer, true, true, false, false, false, "html status return code (i.e. \"200\" for ok), -1 if not loaded"),
-/**/httpstatus_redirect_s(SolrType.string, true, true, false, false, false, "redirect url if the error code is 299 < httpstatus_i < 310"), // TODO: delete candidate, not used so far (2014-12-26)
-    references_i(SolrType.num_integer, true, true, false, false, false, "number of unique http references, should be equal to references_internal_i + references_external_i"),
-    references_internal_i(SolrType.num_integer, true, true, false, false, false, "number of unique http references from same host to referenced url"),
-    references_external_i(SolrType.num_integer, true, true, false, false, false, "number of unique http references from external hosts"),
-    references_exthosts_i(SolrType.num_integer, true, true, false, false, false, "number of external hosts which provide http references"),
-    crawldepth_i(SolrType.num_integer, true, true, false, false, false, "crawl depth of web page according to the number of steps that the crawler did to get to this document; if the crawl was started at a root document, then this is equal to the clickdepth"),
+    /**/httpstatus_redirect_s(SolrType.string, true, true, false, false, false, "redirect url if the error code is 299 < httpstatus_i < 310"), // TODO: delete candidate, not used so far (2014-12-26)
     process_sxt(SolrType.string, true, true, true, false, false, "needed (post-)processing steps on this metadata set"),
-    harvestkey_s(SolrType.string, true, true, false, false, false, "key from a harvest process (i.e. the crawl profile hash key) which is needed for near-realtime postprocessing. This shall be deleted as soon as postprocessing has been terminated."),
     
     // optional but recommended, part of index distribution
-    load_date_dt(SolrType.date, true, true, false, false, false, "time when resource was loaded"),
     fresh_date_dt(SolrType.date, true, true, false, false, false, "date until resource shall be considered as fresh"),
     referrer_id_s(SolrType.string, true, true, false, false, false, "id of the referrer to this document, discovered during crawling"),// byte[] referrerHash();
     publisher_t(SolrType.text_general, true, true, false, false, true, "the name of the publisher of the document"),// String dc_publisher();
@@ -132,11 +143,7 @@ public enum CollectionSchema implements SchemaDeclaration {
             // bit 16: "unavailable_after" contained in http header X-Robots-Tag
     robots_i(SolrType.num_integer, true, true, false, false, false, "content of <meta name=\"robots\" content=#content#> tag and the \"X-Robots-Tag\" HTTP property"),
     metagenerator_t(SolrType.text_general, true, true, false, false, false, "content of <meta name=\"generator\" content=#content#> tag"),
-    inboundlinks_protocol_sxt(SolrType.string, true, true, true, false, false, "internal links, only the protocol"),
-    inboundlinks_urlstub_sxt(SolrType.string, true, true, true, false, true, "internal links, the url only without the protocol"),
     inboundlinks_anchortext_txt(SolrType.text_general, true, true, true, false, true, "internal links, the visible anchor text"),
-    outboundlinks_protocol_sxt(SolrType.string, true, true, true, false, false, "external links, only the protocol"),
-    outboundlinks_urlstub_sxt(SolrType.string, true, true, true, false, true, "external links, the url only without the protocol"),
     outboundlinks_anchortext_txt(SolrType.text_general, true, true, true, false, true, "external links, the visible anchor text"),
     
     icons_urlstub_sxt(SolrType.string, true, true, true, false, true, "all icon links without the protocol and '://'"),
@@ -146,8 +153,6 @@ public enum CollectionSchema implements SchemaDeclaration {
     icons_sizes_sxt(SolrType.num_integer, true, true, true, false, false, "all icon sizes space separated (e.g. '16x16 32x32')"),
     
     images_text_t(SolrType.text_general, true, true, false, false, true, "all text/words appearing in image alt texts or the tokenized url"),
-    images_urlstub_sxt(SolrType.string, true, true, true, false, true, "all image links without the protocol and '://'"),
-    images_protocol_sxt(SolrType.string, true, true, true, false, false, "all image link protocols"),
     images_alt_sxt(SolrType.string, true, true, true, false, true, "all image link alt tag"), // no need to index this; don't turn it into a txt field; use images_text_t instead
     images_height_val(SolrType.num_integer, true, true, true, false, false, "size of images:height"),
     images_width_val(SolrType.num_integer, true, true, true, false, false, "size of images:width"),
@@ -186,7 +191,6 @@ public enum CollectionSchema implements SchemaDeclaration {
     url_protocol_s(SolrType.string, true, true, false, false, false, "the protocol of the url"),
     url_file_name_s(SolrType.string, true, true, false, false, true, "the file name (which is the string after the last '/' and before the query part from '?' on) without the file extension"),
     url_file_name_tokens_t(SolrType.text_general, true, true, false, false, true, "tokens generated from url_file_name_s which can be used for better matching and result boosting"),
-    url_file_ext_s(SolrType.string, true, true, false, false, true, "the file name extension"),
     url_paths_count_i(SolrType.num_integer, true, true, false, false, false, "number of all path elements in the url hpath (see: http://www.ietf.org/rfc/rfc1738.txt) without the file name"),
     url_paths_sxt(SolrType.string, true, true, true, false, true, "all path elements in the url hpath (see: http://www.ietf.org/rfc/rfc1738.txt) without the file name"),
     url_parameter_i(SolrType.num_integer, true, true, false, false, false, "number of key-value pairs in search part of the url"),
@@ -194,9 +198,7 @@ public enum CollectionSchema implements SchemaDeclaration {
     url_parameter_value_sxt(SolrType.string, true, true, true, false, false, "the values from key-value pairs in the search part of the url"),
     url_chars_i(SolrType.num_integer, true, true, false, false, false, "number of all characters in the url == length of sku field"),
 
-    host_s(SolrType.string, true, true, false, false, true, "host of the url"),
     host_dnc_s(SolrType.string, true, true, false, false, true, "the Domain Class Name, either the TLD or a combination of ccSLD+TLD if a ccSLD is used."),
-    host_organization_s(SolrType.string, true, true, false, false, true, "either the second level domain or, if a ccSLD is used, the third level domain"),
     host_organizationdnc_s(SolrType.string, true, true, false, false, true, "the organization and dnc concatenated with '.'"),
     host_subdomain_s(SolrType.string, true, true, false, false, true, "the remaining part of the host without organizationdnc"),
     host_extent_i(SolrType.num_integer, true, true, false, false, false, "number of documents from the same host; can be used to measure references_internal_i for likelihood computation"),
@@ -260,8 +262,15 @@ public enum CollectionSchema implements SchemaDeclaration {
     private final SolrType type;
     private final boolean indexed, stored, searchable, multiValued, omitNorms, docValues;
     private String comment;
-
+    
+    /** When true, the field must be enabled for proper YaCy operation */
+    private boolean mandatory = false;
+    
     private CollectionSchema(final SolrType type, final boolean indexed, final boolean stored, final boolean multiValued, final boolean omitNorms, final boolean searchable, final String comment) {
+        this(type, indexed, stored, multiValued, omitNorms, searchable, comment, false);
+    }
+
+    private CollectionSchema(final SolrType type, final boolean indexed, final boolean stored, final boolean multiValued, final boolean omitNorms, final boolean searchable, final String comment, final boolean mandatory) {
         this.type = type;
         this.indexed = indexed;
         this.stored = stored;
@@ -269,6 +278,7 @@ public enum CollectionSchema implements SchemaDeclaration {
         this.omitNorms = omitNorms;
         this.searchable = searchable;
         this.comment = comment;
+        this.mandatory = mandatory;
         this.docValues = (type == SolrType.string || type == SolrType.date || type.name().startsWith("num_"));
         // verify our naming scheme
         String name = this.name();
@@ -354,6 +364,11 @@ public enum CollectionSchema implements SchemaDeclaration {
         return this.comment;
     }
     
+    @Override
+    public final boolean isMandatory() {
+    	return this.mandatory;
+    }
+    
     @Override
     public final void add(final SolrInputDocument doc, final String value) {
         assert !this.isMultiValued();
diff --git a/source/net/yacy/search/schema/WebgraphSchema.java b/source/net/yacy/search/schema/WebgraphSchema.java
index ef5f4ae6b..9f4b6ad55 100644
--- a/source/net/yacy/search/schema/WebgraphSchema.java
+++ b/source/net/yacy/search/schema/WebgraphSchema.java
@@ -200,6 +200,11 @@ public enum WebgraphSchema implements SchemaDeclaration {
     public final String getComment() {
         return this.comment;
     }
+    
+    @Override
+    public boolean isMandatory() {
+    	return false;
+    }
 
     @Override
     public final void add(final SolrInputDocument doc, final String value) {