Upgrade prerequisite checks

The following prerequisite checks are automatically run by the upgrade procedure on the BigFix Server.

If any of these checks fails, the upgrade does not start and the procedure exits with an error message. You can rerun the upgrade after you ensure that the condition that failed is satisfied. The upgrade procedure checks that:

The size of the Upload Manager Buffer Directory and the number of files that it contains do not exceed the 90% of the values that are specified in the following settings:
```
_BESRelay_UploadManager_BufferDirectoryMaxSize
_BESRelay_UploadManager_BufferDirectoryMaxCount
```
If the check fails: Fix the issue by running the following Fixlets available in the BES Support site, and then rerun the upgrade:
```
2695: WARNING: Upload Manager Directory exceeds file max number - BES Server
2696: WARNING: Upload Manager Directory Full - BES Server
```
The site names listed in the following columns of the database contain only ASCII characters:
```
LOCAL_OBJECT_DEFS.Name 
LOCAL_OBJECT_DEFS.Sitename
```
If the check fails: Rename the site names and fix the content referencing them.
The size of the data related to custom content and the actions that are contained in the ACTION_DEFS.Fields and LOCAL_OBJECT_DEFS.Fields fields does not exceed the maximum size allowed in the new database schema.
If the check fails: Shorten the exceeding data length.
If you are using DB2, the table spaces hosting the following tables have enough disk space available to store the WebUI indexes:
```
COMPUTERS
VERSIONS
DASHBOARDDATA
EXTERNAL_ANALYSIS_PROPERTY_TRANSLATIONS
EXTERNAL_ANALYSIS_TRANSLATIONS   
EXTERNAL_FIXLET_ACTION_SETTINGS_USER_GROUPS
EXTERNAL_FIXLET_TRANSLATIONS
```
If the check fails: Move the tables to USERSPACE1. For information about how to accomplish this task, see https://www.ibm.com/support/knowledgecenter/en/SSEPGG_10.5.0/com.ibm.db2.luw.sql.rtn.doc/doc/r0055069.html.
The number of rows contained in the DBINFO database table does not exceed one.
If the check fails: Remove the unnecessary rows from the table.
The data contained in each of the following fields does not exceed the maximum index length:
```
DASHBOARDDATA.NAME
UNMANAGEDASSET_FIELDS_TYPES.FIELDNAME
WEBUI_DATA.NAME
```
If the check fails: Shorten the data contained in the fields as required.

If you are in a DSA environment and any of the prerequisite checks fails on the primary server, which is the first one to be upgraded, run these steps:

Run the needed corrective actions on the primary server.
Wait for a full replica on the secondary servers to ensure that the same corrective actions are applied to their databases as well.
After the full replica completes, rerun the upgrade on the primary server and then on the secondary servers.