I have a trigger that runs on the User object that updates many Cases in bulk depending on if the User exists in one of several fields on the Case. I run into issues when trying to run this on multiple User records at once, if the # of Cases exceeds 10,000 (due to SF governor limits). I'd like to break this out and use batch Apex - but I'm not sure how I convert this trigger into Batch Apex.

Here is the trigger code. I just need some help getting started on breaking this out into Batch. thanks!

trigger UpdatePTOonCase on User (after update) {

// this trigger updates the NSR PTO fields on Enterprise Cases based on changes to the NSR flag on the User record.

Set userIds = new Set();

List users = Trigger.new;

//list to hold cases that will need to be updated

 List casesToUpdate = new List();

 //gather all user ids in the update in a set

for (User u : users) {

userids.add(u.id); }

 // grab all open cases where this users is one of the related nsr's and place in map

Map cMap = new Map([SELECT id, nsr_lookup__c, BI_nsr_lookup__c, Tech_nsr_lookup__c, Time_nsr_lookup__c, Talent_nsr_lookup__c FROM Case WHERE isClosed = false AND (nsr_lookup__c in: userids OR BI_NSR_Lookup__c in: userids OR Tech_nsr_lookup__c in: userids OR Talent_nsr_lookup__c in: userids OR Time_nsr_lookup__c in: userids)]);

//create list of cases List cases

List = cmap.values();

//create set of case id's

Set caseids = cMap.keyset();

for (User u : users) {

User old = trigger.oldMap.get(u.id);

 if (old.PTO__c != u.PTO__c) {

 //loop through Case list and add case id's

for (Case c :casesList) {

 if (c.nsr_lookup__c == u.id) {

//set NSR PTO Field on Case

c.nsr_pto__c = u.PTO__c; }

 if (c.BI_nsr_lookup__c == u.id) {

//set NSR PTO Field on Case

c.BI_nsr_pto__c = u.PTO__c; }

if (c.Tech_nsr_lookup__c == u.id) {

//set NSR PTO Field on Case

 c.Tech_nsr_pto__c = u.PTO__c; }

 if (c.Time_nsr_lookup__c == u.id) {

 //set NSR PTO Field on Case

c.Time_nsr_pto__c = u.PTO__c; }

 if (c.Talent_nsr_lookup__c == u.id) {

 //set NSR PTO Field on Case

c.Talent_nsr_pto__c = u.PTO__c; }

casesToUpdate.add(c); } } }

//call method to prevent case triggers from firing

 PreventRecursive.setUpdatedFromUser ();

update casesToUpdate ; }