diff --git a/plugins/libkolab/SQL/mysql.initial.sql b/plugins/libkolab/SQL/mysql.initial.sql
index 2aa046d7..98e7e78d 100644
--- a/plugins/libkolab/SQL/mysql.initial.sql
+++ b/plugins/libkolab/SQL/mysql.initial.sql
@@ -31,7 +31,7 @@ CREATE TABLE `kolab_cache_contact` (
   `changed` DATETIME DEFAULT NULL,
   `data` LONGTEXT NOT NULL,
   `xml` LONGBLOB NOT NULL,
-  `tags` VARCHAR(255) NOT NULL,
+  `tags` TEXT NOT NULL,
   `words` TEXT NOT NULL,
   `type` VARCHAR(32) CHARACTER SET ascii NOT NULL,
   `name` VARCHAR(255) NOT NULL,
@@ -55,7 +55,7 @@ CREATE TABLE `kolab_cache_event` (
   `changed` DATETIME DEFAULT NULL,
   `data` LONGTEXT NOT NULL,
   `xml` LONGBLOB NOT NULL,
-  `tags` VARCHAR(255) NOT NULL,
+  `tags` TEXT NOT NULL,
   `words` TEXT NOT NULL,
   `dtstart` DATETIME,
   `dtend` DATETIME,
@@ -75,7 +75,7 @@ CREATE TABLE `kolab_cache_task` (
   `changed` DATETIME DEFAULT NULL,
   `data` LONGTEXT NOT NULL,
   `xml` LONGBLOB NOT NULL,
-  `tags` VARCHAR(255) NOT NULL,
+  `tags` TEXT NOT NULL,
   `words` TEXT NOT NULL,
   `dtstart` DATETIME,
   `dtend` DATETIME,
@@ -95,7 +95,7 @@ CREATE TABLE `kolab_cache_journal` (
   `changed` DATETIME DEFAULT NULL,
   `data` LONGTEXT NOT NULL,
   `xml` LONGBLOB NOT NULL,
-  `tags` VARCHAR(255) NOT NULL,
+  `tags` TEXT NOT NULL,
   `words` TEXT NOT NULL,
   `dtstart` DATETIME,
   `dtend` DATETIME,
@@ -115,7 +115,7 @@ CREATE TABLE `kolab_cache_note` (
   `changed` DATETIME DEFAULT NULL,
   `data` LONGTEXT NOT NULL,
   `xml` LONGBLOB NOT NULL,
-  `tags` VARCHAR(255) NOT NULL,
+  `tags` TEXT NOT NULL,
   `words` TEXT NOT NULL,
   CONSTRAINT `fk_kolab_cache_note_folder` FOREIGN KEY (`folder_id`)
     REFERENCES `kolab_folders`(`folder_id`) ON DELETE CASCADE ON UPDATE CASCADE,
@@ -133,7 +133,7 @@ CREATE TABLE `kolab_cache_file` (
   `changed` DATETIME DEFAULT NULL,
   `data` LONGTEXT NOT NULL,
   `xml` LONGBLOB NOT NULL,
-  `tags` VARCHAR(255) NOT NULL,
+  `tags` TEXT NOT NULL,
   `words` TEXT NOT NULL,
   `filename` varchar(255) DEFAULT NULL,
   CONSTRAINT `fk_kolab_cache_file_folder` FOREIGN KEY (`folder_id`)
@@ -153,7 +153,7 @@ CREATE TABLE `kolab_cache_configuration` (
   `changed` DATETIME DEFAULT NULL,
   `data` LONGTEXT NOT NULL,
   `xml` LONGBLOB NOT NULL,
-  `tags` VARCHAR(255) NOT NULL,
+  `tags` TEXT NOT NULL,
   `words` TEXT NOT NULL,
   `type` VARCHAR(32) CHARACTER SET ascii NOT NULL,
   CONSTRAINT `fk_kolab_cache_configuration_folder` FOREIGN KEY (`folder_id`)
@@ -173,7 +173,7 @@ CREATE TABLE `kolab_cache_freebusy` (
   `changed` DATETIME DEFAULT NULL,
   `data` LONGTEXT NOT NULL,
   `xml` LONGBLOB NOT NULL,
-  `tags` VARCHAR(255) NOT NULL,
+  `tags` TEXT NOT NULL,
   `words` TEXT NOT NULL,
   `dtstart` DATETIME,
   `dtend` DATETIME,
@@ -184,4 +184,4 @@ CREATE TABLE `kolab_cache_freebusy` (
 ) /*!40000 ENGINE=INNODB */ /*!40101 CHARACTER SET utf8 COLLATE utf8_general_ci */;
 
 
-INSERT INTO `system` (`name`, `value`) VALUES ('libkolab-version', '2014021000');
+INSERT INTO `system` (`name`, `value`) VALUES ('libkolab-version', '2015011600');
diff --git a/plugins/libkolab/SQL/mysql/2015011600.sql b/plugins/libkolab/SQL/mysql/2015011600.sql
new file mode 100644
index 00000000..be523aef
--- /dev/null
+++ b/plugins/libkolab/SQL/mysql/2015011600.sql
@@ -0,0 +1,8 @@
+ALTER TABLE `kolab_cache_contact` MODIFY `tags` text NOT NULL;
+ALTER TABLE `kolab_cache_event` MODIFY `tags` text NOT NULL;
+ALTER TABLE `kolab_cache_task` MODIFY `tags` text NOT NULL;
+ALTER TABLE `kolab_cache_journal` MODIFY `tags` text NOT NULL;
+ALTER TABLE `kolab_cache_note` MODIFY `tags` text NOT NULL;
+ALTER TABLE `kolab_cache_file` MODIFY `tags` text NOT NULL;
+ALTER TABLE `kolab_cache_configuration` MODIFY `tags` text NOT NULL;
+ALTER TABLE `kolab_cache_freebusy` MODIFY `tags` text NOT NULL;
diff --git a/plugins/libkolab/SQL/oracle.initial.sql b/plugins/libkolab/SQL/oracle.initial.sql
index 073dad56..8f1ed644 100644
--- a/plugins/libkolab/SQL/oracle.initial.sql
+++ b/plugins/libkolab/SQL/oracle.initial.sql
@@ -36,7 +36,7 @@ CREATE TABLE "kolab_cache_contact" (
     "changed" timestamp DEFAULT NULL,
     "data" clob NOT NULL,
     "xml" clob NOT NULL,
-    "tags" varchar(255) DEFAULT NULL,
+    "tags" clob DEFAULT NULL,
     "words" clob DEFAULT NULL,
     "type" varchar(32) NOT NULL,
     "name" varchar(255) DEFAULT NULL,
@@ -59,7 +59,7 @@ CREATE TABLE "kolab_cache_event" (
     "changed" timestamp DEFAULT NULL,
     "data" clob NOT NULL,
     "xml" clob NOT NULL,
-    "tags" varchar(255) DEFAULT NULL,
+    "tags" clob DEFAULT NULL,
     "words" clob DEFAULT NULL,
     "dtstart" timestamp DEFAULT NULL,
     "dtend" timestamp DEFAULT NULL,
@@ -78,7 +78,7 @@ CREATE TABLE "kolab_cache_task" (
     "changed" timestamp DEFAULT NULL,
     "data" clob NOT NULL,
     "xml" clob NOT NULL,
-    "tags" varchar(255) DEFAULT NULL,
+    "tags" clob DEFAULT NULL,
     "words" clob DEFAULT NULL,
     "dtstart" timestamp DEFAULT NULL,
     "dtend" timestamp DEFAULT NULL,
@@ -97,7 +97,7 @@ CREATE TABLE "kolab_cache_journal" (
     "changed" timestamp DEFAULT NULL,
     "data" clob NOT NULL,
     "xml" clob NOT NULL,
-    "tags" varchar(255) DEFAULT NULL,
+    "tags" clob DEFAULT NULL,
     "words" clob DEFAULT NULL,
     "dtstart" timestamp DEFAULT NULL,
     "dtend" timestamp DEFAULT NULL,
@@ -116,7 +116,7 @@ CREATE TABLE "kolab_cache_note" (
     "changed" timestamp DEFAULT NULL,
     "data" clob NOT NULL,
     "xml" clob NOT NULL,
-    "tags" varchar(255) DEFAULT NULL,
+    "tags" clob DEFAULT NULL,
     "words" clob DEFAULT NULL,
     PRIMARY KEY ("folder_id", "msguid")
 );
@@ -133,7 +133,7 @@ CREATE TABLE "kolab_cache_file" (
     "changed" timestamp DEFAULT NULL,
     "data" clob NOT NULL,
     "xml" clob NOT NULL,
-    "tags" varchar(255) DEFAULT NULL,
+    "tags" clob DEFAULT NULL,
     "words" clob DEFAULT NULL,
     "filename" varchar(255) DEFAULT NULL,
     PRIMARY KEY ("folder_id", "msguid")
@@ -152,7 +152,7 @@ CREATE TABLE "kolab_cache_configuration" (
     "changed" timestamp DEFAULT NULL,
     "data" clob NOT NULL,
     "xml" clob NOT NULL,
-    "tags" varchar(255) DEFAULT NULL,
+    "tags" clob DEFAULT NULL,
     "words" clob DEFAULT NULL,
     "type" varchar(32) NOT NULL,
     PRIMARY KEY ("folder_id", "msguid")
@@ -171,7 +171,7 @@ CREATE TABLE "kolab_cache_freebusy" (
     "changed" timestamp DEFAULT NULL,
     "data" clob NOT NULL,
     "xml" clob NOT NULL,
-    "tags" varchar(255) DEFAULT NULL,
+    "tags" clob DEFAULT NULL,
     "words" clob DEFAULT NULL,
     "dtstart" timestamp DEFAULT NULL,
     "dtend" timestamp DEFAULT NULL,
@@ -181,4 +181,4 @@ CREATE TABLE "kolab_cache_freebusy" (
 CREATE INDEX "kolab_cache_fb_uid2msguid" ON "kolab_cache_freebusy" ("folder_id", "uid", "msguid");
 
 
-INSERT INTO "system" ("name", "value") VALUES ('libkolab-version', '2014021000');
+INSERT INTO "system" ("name", "value") VALUES ('libkolab-version', '2015011600');
diff --git a/plugins/libkolab/SQL/oracle/2015011600.sql b/plugins/libkolab/SQL/oracle/2015011600.sql
new file mode 100644
index 00000000..69f79538
--- /dev/null
+++ b/plugins/libkolab/SQL/oracle/2015011600.sql
@@ -0,0 +1,40 @@
+-- direct change from varchar to clob does not work, need temp column (#4257)
+ALTER TABLE "kolab_cache_contact" ADD "tags1" clob DEFAULT NULL;
+UPDATE "kolab_cache_contact" SET "tags1" = "tags";
+ALTER TABLE "kolab_cache_contact" DROP COLUMN "tags";
+ALTER TABLE "kolab_cache_contact" RENAME COLUMN "tags1" TO "tags";
+
+ALTER TABLE "kolab_cache_event" ADD "tags1" clob DEFAULT NULL;
+UPDATE "kolab_cache_event" SET "tags1" = "tags";
+ALTER TABLE "kolab_cache_event" DROP COLUMN "tags";
+ALTER TABLE "kolab_cache_event" RENAME COLUMN "tags1" TO "tags";
+
+ALTER TABLE "kolab_cache_task" ADD "tags1" clob DEFAULT NULL;
+UPDATE "kolab_cache_task" SET "tags1" = "tags";
+ALTER TABLE "kolab_cache_task" DROP COLUMN "tags";
+ALTER TABLE "kolab_cache_task" RENAME COLUMN "tags1" TO "tags";
+
+ALTER TABLE "kolab_cache_journal" ADD "tags1" clob DEFAULT NULL;
+UPDATE "kolab_cache_journal" SET "tags1" = "tags";
+ALTER TABLE "kolab_cache_journal" DROP COLUMN "tags";
+ALTER TABLE "kolab_cache_journal" RENAME COLUMN "tags1" TO "tags";
+
+ALTER TABLE "kolab_cache_note" ADD "tags1" clob DEFAULT NULL;
+UPDATE "kolab_cache_note" SET "tags1" = "tags";
+ALTER TABLE "kolab_cache_note" DROP COLUMN "tags";
+ALTER TABLE "kolab_cache_note" RENAME COLUMN "tags1" TO "tags";
+
+ALTER TABLE "kolab_cache_file" ADD "tags1" clob DEFAULT NULL;
+UPDATE "kolab_cache_file" SET "tags1" = "tags";
+ALTER TABLE "kolab_cache_file" DROP COLUMN "tags";
+ALTER TABLE "kolab_cache_file" RENAME COLUMN "tags1" TO "tags";
+
+ALTER TABLE "kolab_cache_configuration" ADD "tags1" clob DEFAULT NULL;
+UPDATE "kolab_cache_configuration" SET "tags1" = "tags";
+ALTER TABLE "kolab_cache_configuration" DROP COLUMN "tags";
+ALTER TABLE "kolab_cache_configuration" RENAME COLUMN "tags1" TO "tags";
+
+ALTER TABLE "kolab_cache_freebusy" ADD "tags1" clob DEFAULT NULL;
+UPDATE "kolab_cache_freebusy" SET "tags1" = "tags";
+ALTER TABLE "kolab_cache_freebusy" DROP COLUMN "tags";
+ALTER TABLE "kolab_cache_freebusy" RENAME COLUMN "tags1" TO "tags";