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The Lotus Notes Error: “Category Must be Single String”- How to Troubleshoot and Recover

Posted In Software Reviews - By Techtiplib on Wednesday, September 17th, 2014 With No Comments »

Lotus Notes, is a collaborative business application, which serves the purpose of web browsing, accessing business emails, instant messaging and calendars. Information in Lotus Notes is stored in the Network Storage format (.NSF). Sometimes, there is corruption of the database, which causes inaccessibility of such components like emails. This will lead to throwing of some errors by Lotus Notes. A Lotus Notes recovery software is used, when all other recovery options fail.

Lotus Notes recovery - error

One of the errors, which happen when a document is opened in Lotus Notes, is:

“Category must be single string”


This error arises due to embedded views. In fact, if we want to be more exact, then the reason is the sorted category is not text and the document contains an embedded view.


We can add @Text formula to the sorted column formula, in the embedded view with


@Text formula is added to the Show Single Category object of the embedded view, if there is a Single Category View of the document that is in use.

The key words entered by the user of the document, can be categorized.

If the embedded view is to be simulated, then we can resort to FTSearch, with each line corresponding to a document that was found as a result of search. The full text searching on the database can be done with the help of the Search bar on the client for Notes or the use of db.FTSearch, associated with the Lotus Scripts.

The corruption of the NSF files can be a reason for such an error. One of the causes of database corruption is due to such reason like a corrupted metadata of the file, which defines the database file. Another reason is due to the corruption in the content and not the structure of the database.

A probable solution for this might be reduction in the exposure to the database corruption. One such measure in the Domino environment is the enabling of all the servers with the transaction logging procedure. The transaction log maintains the records of all the transactions related to the database. In case of a system failure, these are used for the restoration and the database recovery, without the wastage of the restart time for the server.

There are two aspects of the styles of transaction logging, which are installed on the server. These are Archival logging or the Restart Recovery. Archival logging can lead to the restoration of the lost contents. Restart Recover is a common option for all types of transaction logging. The transactions, which were not flushed to the disk, while a database crash occurred, are brought back to maintain the consistency of the database.

Database Repair

The restoration of the database can be done with the help of some tools, which are discussed next. These are:


We need to fix the type of database, which is run against the task. When the target of maintenance is a Systems database, then the associated tasks with it are needed to be stopped. Domino log or the Domino directory can also be a target of maintenance. In such a situation, it is needed that the Domino server be stopped and offline maintenance activities are to be run. While running ‘Fixup’ for non-system databases, the user does not require the stoppage of the tasks. The user’s mail database is an example of the non-system database.


This is the most appropriate tool, when the database view or views are corrupted. Lookups against the view may get impacted, till the completion of the task is done.

Updall is similar to update but without continuous running or working from a queue. It can rebuild all the full-text search indexes or corrupt view indexes.

If we run Updall daily, then the disk space can be saved, with the help of discard of unused view indexes or the purging of deletion stubs. 


With the deletion of documents or attachments of the database, Dominos reuses the unused space instead of a size reduction for the files. The Compact Utility also requires the determination of the type of database. There are three styles of compacting.

These are:

  • In-place compacting with recovery of space
  • In-place compacting which results in the recovery of space and reduction in file size
  • Copy-style compacting

A copy-style compact is performed on the corrupted database. The copy-style compacting creates copies of database and the original file is deleted, after the completion of the compaction. This type of compaction requires that there are no accessing processes within the duration of the task. These will be terminated if the database is being opened due to a read or write operation. The users of the database and the tasks associated with the database are not accessible by the database. This type of compaction will start with a database instant id (DBIID). The user needs to make a full backup, after the compaction procedure is over. The recommended view is to compact the databases, either weekly or monthly for the recovery of the disk spaces.

If the above Utilities fail to repair the database, then the commercial software comes into picture. One such advanced software is Stellar Phoenix Lotus Notes Recovery. This enables the NSF recovery in a precise manner. It can save the NSF files in a specified location including the network disc. It can lead to the recovery of the emails, attachments, OLE objects and Java Applets.

Author Bio:

Amanda Lakai has been writing as a freelancer blogger since last three years. She is passionate to explore about the various Email recovery tips & tricks and various Email converter tools such as: Thunderbird Mail Recovery, Lotus Notes recovery, Zarafa Recovery, GroupWise to Exchange Migrator, NSF to PST Converter and GroupWise to PST Converter etc. She loves to share her findings with the readers So that, they can enhance their knowledge-base and also use them in their daily life if required.

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