In development server, due to the fact that process design will always get updated and developed, there will be more and more XPDLs cached in the memory. In the long run, this may cause "java.lang.OutOfMemoryError" exception during runtime or server startup. To solve this issue, we will need to clean up the unused XPDLs with following steps. The following example queries are written in MySQL and MSSQL syntax.

1. Check existing count of XPDLs

On a common production server, normally there are only few app versions and each version only tied to 1 process version. This is because we won't do any development in production server, so the process version is only increased during the app imported. But in the development server, it will be a different case. The process version will be going up to few hundred process version which also means there are few hundred of XPDL data are cached in memory. To check how many XPDLs are cached, please run the following query in your database server.

 select count(*) from SHKXPDLS

2. Check the count of unused XPDLs

In all the cached process version XPDLs, there is a case that some process version is not used by any process instances. These unused XPDLs can be safely deleted. The check the number of unused XPDLs, we can use the following query. Then, we can know how many are unused in the total number of XPDLs.

...

select * from SHKXPDLS x
where concat(x.XPDLId, x.XPDLVersion) not in (
    select concat(packageId,packageVersion) as id from (
        select def.PackageId as packageId, TO_CHAR(def.ProcessDefinitionVersion) as packageVersion 
        from SHKActivities act 
        join SHKProcesses pro on act.Process = pro.oid 
        left join SHKProcessDefinitions def on pro.ProcessDefinition = def.oid 
        group by def.PackageId, def.ProcessDefinitionVersion 
        union 
        select packageId, TO_CHAR(packageVersion) from app_package
    ) group by packageId, packageVersion
);

3. Delete completed process instances data to clean up more XPDLs from cache

If the process instances data are not important to you or you have your process instance data captured a copy by the Process Data Collector plugin, you can delete your process instances data to increase the number of unused XPDLs. In this case, only the process version for running process instances and the latest process version for each app version will be kept.

...

delete from SHKAssignmentsTable;
delete from SHKAndJoinTable;
delete from SHKDeadlines;
delete from SHKActivityData;
delete from SHKActivities;
delete from SHKProcessData;
delete from SHKProcessRequesters;
delete from SHKProcesses;

4. Delete the unused XDPLs

Now, you can delete the unused XPDLs and it will be free from your memory cache when next server startup.

...