# Limitations

When defining a task with Google Cloud Pub/Sub as the target endpoint, the following limitations apply:

* The Google Cloud Pub/Sub target endpoint does not support unlimited LOB size. Therefore, when replicating from source tables with LOB columns, *do not* select the Allow unlimited LOB size option.

  For more information on defining LOB settings, see [Target metadata](https://help.qlik.com/en-US/replicate/May2026/Content/Global_Common/Content/SharedEMReplicate/Customize%20Tasks/target_metadata.htm).

* Batch optimized apply mode is not supported. If this mode is set, the task will automatically switch to Transactional apply mode and a message will be written to the task's log file.

  For more information on these modes, see [Change Processing Tuning](https://help.qlik.com/en-US/replicate/May2026/Content/Global_Common/Content/SharedEMReplicate/Customize%20Tasks/tasks_applychangtunestab.htm).

* Store Changes mode is not supported.

* Google Cloud Pub/Sub topic names must adhere to the guidelines provided in [Create and manage topics](https://cloud.google.com/pubsub/docs/create-topic#resource_names).

  If the source table names exceed the maximum permitted length or contain unsupported characters, you need to do one of the following:

  * Modify the names before starting the task.
  * Define a table-level transformation if only a single table name needs to be changed.
  * Define a global transformation rule for multiple tables. For information on defining global transformations, see [Starting the Global Transformation Rules wizard](https://help.qlik.com/en-US/replicate/May2026/Content/Global_Common/Content/SharedEMReplicate/Customize%20Tasks/tasks_newTransRuleWiz.htm).

* The [Ignore ALTER](https://help.qlik.com/en-US/replicate/May2026/Content/Global_Common/Content/SharedEMReplicate/Customize%20Tasks/tasks_applychangsetstab.htm#ignore_alter) Apply Changes setting is not supported for changes to source data types and table renaming.

* Column names must adhere to the guidelines provided in [Create and manage topics](https://cloud.google.com/pubsub/docs/create-topic#resource_names).

  If a source column name does not adhere to this rule, then [a transformation should be used](https://help.qlik.com/en-US/replicate/May2026/Content/Global_Common/Content/SharedEMReplicate/Customize%20Tasks/tasks_useTransTable.htm) to rename the column.

* The [Drop and Create table](https://help.qlik.com/en-US/replicate/May2026/Content/Global_Common/Content/SharedEMReplicate/Customize%20Tasks/tasks_fullLoadSetstab.htm) Target Table Preparation option is only supported when the endpoint is configured to create a separate topic for each table. When the Drop and Create table option is set, the associated subscription will also be deleted.
* The [Truncate before loading](https://help.qlik.com/en-US/replicate/May2026/Content/Global_Common/Content/SharedEMReplicate/Customize%20Tasks/tasks_fullLoadSetstab.htm) Target Table Preparation option is not supported.
* The Change Data Partitioning [Control table](https://help.qlik.com/en-US/replicate/May2026/Content/Replicate/Main/Control%20Tables/control_tables.htm) is not supported.